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Not only the students but also the professor ___ stunned by the test results.
- A. was
- B. were
- C. are
- D. be
Correct Answer: A
Rationale: In this sentence, 'students' and 'professor' are part of a compound subject joined by 'not only...but also,' which makes the subject singular. Since the subjects are singular, the correct verb to use is 'was,' making choice A the correct answer.
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Consumption of food is a universal necessity. Different cultures have developed different methods to accomplish the task. It is interesting to discover these differences and learn new ways
to do things.
European cultures developed cutlery (knives, forks, and spoons) to enable people to efficiently
eat their food. Correct use of this toolÄ€™s changes with the times-what was polite in 1800 may not
be considered proper manners today.
China developed the chopstick as an efficient tool for eating. Mastery of the use of chopsticks can be difficult for the person not raised in the culture. The attempts of a novice to use
chopsticks can be very amusing to the watcher, but frustrating for the hungry diner. Space travel has created new challenges for consuming food. Squeeze bottles and other unique
packaging have enabled space travelers to get their needed nutrition. Chopsticks and forks do not work well in space.
What is the best definition of efficient as used in the third paragraph?
- A. Productive without waste
- B. Cost-effective
- C. Performing well with minimal effort
- D. Optimal use of resources
Correct Answer: A
Rationale: The term 'efficient' in the context of the third paragraph refers to being 'productive without waste.' When something is efficient, it means it is able to achieve maximum productivity with minimal resources or effort. In this case, the chopstick is described as an efficient tool for eating, implying that it allows individuals to consume food effectively without unnecessary wastage. Hence, option A, 'Productive without waste,' best defines the term 'efficient' in this context.
The immune system is a network of cells, tissues, and organs that defends the body against attacks by foreign invaders. These invaders are primarily microbesĆ¢Ä‚¬Ä€¯tiny organisms such as bacteria, parasites, and fungiĆ¢Ä‚¬Ä€¯that can cause infections. Viruses also cause infections, but are too primitive to be classified as living organisms. The human body provides an ideal environment for many microbes. It is the immune systemĆ¢Ä‚¬Ä„¢s job to keep the microbes out or destroy them.
The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can secrete fluids and cells to wipe out nearly all of them. The secret to its success is an elaborate and dynamic communications network. Millions of cells, organized into sets and subsets, gather and transfer information in response to an infection. Once immune cells receive the alarm, they produce powerful chemicals that help to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots.
Although scientists have learned much about the immune system, they continue to puzzle over how the body destroys invading microbes, infected cells, and tumors without harming healthy tissues. New technologies for identifying individual immune cells are now allowing scientists to determine quickly which targets are triggering an immune response.
Improvements in microscopy are permitting the first-ever observations of living B cells, T cells, and other cells as they interact within lymph nodes and other body tissues.
In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response, as well as those that dictate the biology of bacteria, viruses, and parasites. The combination of new technology with expanded genetic information will no doubt reveal even more about how the body protects itself from disease.
What is the meaning of the word 'enlist' as it is used in the second paragraph?
- A. call into service
- B. write down
- C. send away
- D. put across
Correct Answer: A
Rationale: In the second paragraph, 'enlist' is used in the context of immune cells responding to an infection by calling other immune cells into service to address the issue. Therefore, the correct meaning of 'enlist' in this context is 'call into service.' The immune system works by activating and directing different cells to combat threats, highlighting the importance of mobilizing immune cells into action to fight infections.
Doppler Effect
Have you ever wondered why the whistle of a traveling, distant locomotive predicts its approach several yards before anyone actually sees it? Or why an oncoming ambulanceÄ€™s screaming siren is heard momentarily several feet before the ambulance comes into full view, before it passes you, and why its siren is still heard faintly well after the ambulance is out of sight?
What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes place is truly remarkable. In both of these instances, when the train or ambulance moves toward the sound waves in front of it, the sound waves are pulled closer together and have a higher frequency. In either instance, the listener positioned in front of the moving object hears a higher pitch. The ambulance and locomotive are progressively moving away from the sound waves behind them, causing the waves to be farther apart and to have a lower frequency. These fast-approaching modes of transportation distance themselves past the listener, who hears a lower pitch.
Which sound waves have a higher pitch?
- A. Sound waves that are closer together
- B. Sound waves that are farther apart
- C. Sound waves that travel a long distance
- D. Sound waves that travel a short distance
Correct Answer: A
Rationale: The correct answer is A: Sound waves that are closer together. The Doppler Effect explains that when a source of sound is moving towards an observer, the sound waves are compressed, resulting in a higher frequency and thus a higher pitch. This phenomenon occurs when the source of the sound moves closer, causing the waves to be closer together. As the object moves away, the waves stretch out, leading to a lower frequency and a lower pitch. Therefore, sound waves that are closer together have a higher pitch, while those that are farther apart have a lower pitch.
Have you ever wondered why the whistle of a traveling, distant locomotive predicts its approach several yards before anyone actually sees it? Or why an oncoming ambulance's screaming siren is heard momentarily several feet before the ambulance comes into full view, before it passes you, and why its siren is still heard faintly well after the ambulance is out of sight?
What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes place is truly remarkable. In both of these instances, when the train or ambulance moves toward the sound waves in front of it, the sound waves are pulled closer together and have a higher frequency. In either instance, the listener positioned in front of the moving object hears a higher pitch. The ambulance and locomotive are progressively moving away from the sound waves behind them, causing the waves to be farther apart and to have a lower frequency. These fast-approaching modes of transportation distance themselves past the listener, who hears a lower pitch.
What is the main idea of the passage?
- A. Trains and ambulances emit loud noises.
- B. Low-frequency waves produce high-pitched sounds.
- C. High-frequency waves result in low-pitched sounds.
- D. The Doppler Effect explains why sound is heard more strongly initially and then faintly after a moving object has passed.
Correct Answer: D
Rationale: The main idea of the passage is to explain the scientific phenomenon known as the Doppler Effect. The passage describes how when a train or ambulance moves towards a listener, sound waves are compressed, resulting in a higher frequency and pitch. Conversely, as the objects move away, the sound waves stretch, leading to a lower frequency and pitch. The Doppler Effect is the reason why sound is heard louder as the object approaches and then fades as it moves away. This explanation aligns with choice D, making it the correct answer.
Photosynthesis is a process used by plants, algae, and certain bacteria to convert light energy into chemical energy stored in sugar molecules. This process is fundamental to life on Earth as it provides the primary source of energy for nearly all organisms. The energy is captured from sunlight by a pigment in the plants called chlorophyll, which gives plants their green color.
During photosynthesis, carbon dioxide from the air and water from the soil react in the presence of light to form sugars and oxygen. The oxygen is released into the atmosphere, which is crucial for the survival of most life forms on Earth. The sugars produced are used by the plant for energy and growth, storing excess energy as starch.
The process occurs in two main stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, energy from sunlight is absorbed by chlorophyll and converted into stored chemical energy in the form of ATP and NADPH. The Calvin cycle uses the ATP and NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.
Photosynthesis not only sustains plant life but also maintains the atmospheric oxygen levels and is a key factor in the carbon cycle, helping to regulate Earth's climate.
What is the primary function of photosynthesis?
- A. To produce oxygen and nitrogen
- B. To convert light energy into chemical energy
- C. To absorb carbon dioxide from the atmosphere
- D. To release water vapor into the air
Correct Answer: B
Rationale: The primary function of photosynthesis is to convert light energy into chemical energy stored in sugar molecules. During photosynthesis, plants, algae, and certain bacteria use sunlight to synthesize sugars from carbon dioxide and water. This process is essential for providing energy to nearly all organisms on Earth. While photosynthesis releases oxygen into the atmosphere as a byproduct, its main purpose is the conversion of light energy into chemical energy, making choice B the correct answer.