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Imagine you have an element with atomic number 11 and mass number 23. How many neutrons does it have?
- A. 11
- B. 12
- C. 23
- D. 21
Correct Answer: B
Rationale: - The atomic number (Z) of an element is the number of protons in its nucleus. In this case, the element has an atomic number of 11.
- The mass number (A) of an element is the sum of its protons and neutrons. Given that the mass number is 23 and the atomic number is 11, we can calculate the number of neutrons by subtracting the atomic number from the mass number: Neutrons = Mass number - Atomic number = 23 - 11 = 12.
- Therefore, the element with atomic number 11 and mass number 23 has 12 neutrons.
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What is the relationship between the wavelength (λ) and frequency (f) of a wave with a constant speed (v)?
- A. λ = v / f
- B. λ = f / v
- C. λ = vf
- D. λ is independent of f and v
Correct Answer: A
Rationale: The relationship between wavelength (λ), frequency (f), and speed (v) of a wave is given by the formula λ = v / f. This formula is derived from the wave equation v = fλ, where v is the speed of the wave, f is the frequency, and λ is the wavelength. By rearranging the equation, we get λ = v / f, indicating that the wavelength is inversely proportional to the frequency when the speed of the wave is constant. Therefore, choice A, λ = v / f, correctly represents the relationship between wavelength and frequency when the speed of the wave is held constant. Choice B, λ = f / v, is incorrect because it represents an inverse relationship between wavelength and speed, which is not the case. Choice C, λ = vf, is incorrect as it implies a direct relationship between wavelength, frequency, and speed, which is not accurate. Choice D, λ is independent of f and v, is incorrect as both frequency and speed affect the wavelength of a wave, as shown by the correct formula λ = v / f.
Where are most of the body's immune cells located?
- A. Blood
- B. Brain
- C. Skin
- D. Large intestine
Correct Answer: A
Rationale: - The majority of the body's immune cells are located in the blood. Immune cells, such as white blood cells (leukocytes), circulate throughout the body via the bloodstream to detect and fight off infections and foreign invaders.
- While immune cells are also present in other parts of the body like the lymph nodes, spleen, and bone marrow, the blood serves as a primary conduit for immune cells to travel to different tissues and organs to carry out their functions.
- The brain (option B) is protected by the blood-brain barrier, which limits the entry of immune cells into the brain to prevent inflammation and damage.
- The skin (option C) contains immune cells like Langerhans cells that help protect against pathogens, but the largest concentration of immune cells is found in the blood.
- The large intestine (option D) also houses a significant amount of immune cells due to its role in interacting with the external environment through the gut-associated lymphoid tissue, but the primary location for most of the body's immune cells is the blood.
During which phase of the cell cycle does DNA replication occur?
- A. Interphase
- B. Mitosis
- C. Meiosis
- D. Cytokinesis
Correct Answer: A
Rationale: Interphase is the phase of the cell cycle where the cell spends the majority of its time and is characterized by three subphases: G1 (Gap 1), S (Synthesis), and G2 (Gap 2). DNA replication specifically occurs during the S phase of interphase. This is a crucial step as it ensures that each daughter cell produced during cell division receives an exact copy of the genetic material. Mitosis is responsible for the equal distribution of the replicated DNA to the daughter cells during cell division. Meiosis is a specialized cell division process for gamete production in sexually reproducing organisms, involving two rounds of division to generate haploid cells. Cytokinesis is the final step of the cell cycle, where the cytoplasm divides to complete the formation of two separate daughter cells following nuclear division.
What is the strongest evidence for evolution?
- A. The fossil record
- B. Comparative anatomy
- C. Biogeography
- D. All of the above
Correct Answer: D
Rationale: A) The fossil record provides evidence of how organisms have changed over time, showing transitional forms and the progression of species.
B) Comparative anatomy involves studying the similarities and differences in the structures of different species, which can reveal common ancestry and evolutionary relationships.
C) Biogeography examines the distribution of species around the world, which can be explained by evolution and continental drift.
By considering all of the above evidence together, scientists can build a comprehensive understanding of evolution and how species have changed and diversified over time.
What happens when the diaphragm contracts?
- A. Air is expelled from the lungs.
- B. The lungs expand to allow air intake.
- C. The vocal cords vibrate to produce sound.
- D. The trachea narrows to control airflow.
Correct Answer: B
Rationale: When the diaphragm contracts, it moves downward, creating more space in the chest cavity. This expansion of the chest cavity causes the lungs to expand as well, allowing air to be drawn into the lungs during inhalation. Therefore, the correct answer is that the lungs expand to allow air intake when the diaphragm contracts. Choices A, C, and D are incorrect because when the diaphragm contracts, it does not expel air from the lungs, cause the vocal cords to vibrate, or narrow the trachea to control airflow.