Nokea
A substance is only considered acidic if it has a pH less than what?
- A. 12
- B. 9
- C. 7
- D. 4
Correct Answer: C
Rationale: A substance is considered acidic if its pH is less than 7. pH values below 7 indicate acidity, while pH values above 7 indicate alkalinity or basicity. Substances with a pH less than 7 are categorized as acidic, not above it. Therefore, a substance is classified as acidic if its pH is less than 7, making choice C the correct answer. Choices A, B, and D are incorrect because a pH of 12, 9, and 4, respectively, are all above 7, and therefore not indicative of acidity.
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Which of the following is a constant?
- A. The number of protons in an oxygen atom
- B. The temperature at which iron ore will melt
- C. The human population size
- D. The time the sun rises each day
Correct Answer: A
Rationale: The number of protons in an oxygen atom is a constant. This value is determined by the atomic number of the element and does not change regardless of the isotope of oxygen. The number of protons defines the element and remains consistent under normal conditions. Choices B, C, and D are not constants. The temperature at which iron ore will melt can vary depending on factors like pressure, the human population size is constantly changing, and the time the sun rises each day varies with the seasons and location.
Which blood vessel carries oxygenated blood back to the heart?
- A. Pulmonary vein
- B. Pulmonary artery
- C. Aorta
- D. Superior vena cava
Correct Answer: A
Rationale: The corrected question is asking for a blood vessel that carries oxygenated blood back to the heart. The pulmonary vein is the correct choice as it carries oxygenated blood from the lungs back to the heart during systemic circulation. The pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation. The aorta is the main artery that carries oxygenated blood away from the heart to the body. The superior vena cava returns deoxygenated blood from the upper body back to the heart.
What would be an appropriate control variable for this experiment?
- A. The period
- B. The length of the string
- C. The mass of the ball
- D. The color of the ball
Correct Answer: C
Rationale: The mass of the ball would be an appropriate control variable for this experiment. By keeping the mass constant, you can ensure that any observed effects are not due to variations in mass but rather to the manipulated independent variable. Controlling the mass helps isolate and identify the true impact of the independent variable being studied. Choices A, B, and D are incorrect. The period and length of the string are more likely to be independent variables or factors being manipulated in the experiment. The color of the ball is considered an extraneous variable that is not typically controlled for in this type of experiment.
Which of the following best describes a plane that divides the body into upper and lower portions?
- A. Coronal
- B. Transverse
- C. Oblique
- D. Median
Correct Answer: B
Rationale: The correct answer is B: Transverse. A transverse plane, also known as a horizontal plane, divides the body into upper and lower portions. This plane is perpendicular to the long axis of the body. Coronal planes divide the body into anterior and posterior portions. Oblique planes pass through the body at an angle, neither strictly horizontal nor vertical. The median plane passes longitudinally through the body, dividing it into equal left and right halves.
Which term describes the allele for green eyes?
- A. Dominant
- B. Recessive
- C. Homozygous
- D. Heterozygous
Correct Answer: B
Rationale: The correct answer is 'B: Recessive.' In genetics, eye color is determined by multiple genes, with green eyes often being associated with a recessive allele. When an individual carries two copies of the recessive allele for green eyes, they will express this eye color. Dominant alleles are expressed over recessive alleles. Homozygous refers to having two identical alleles for a particular gene, and heterozygous refers to having two different alleles. In this context, the allele for green eyes is recessive, meaning it is expressed only when an individual carries two copies of this specific allele. Therefore, 'Recessive' is the most appropriate term to describe the allele for green eyes, making it the correct answer.