What is the author's primary purpose in writing the essay?

Correct Answer: C

Rationale: The author's primary purpose in writing the essay is to inform the reader about how an electrocardiograph reads the electric currents emitted by the heart. Choice A is incorrect because there is no attempt to persuade the reader to have an ECG. Choice B is incorrect because the essay is focused on providing information rather than entertaining with a heartwarming story. Choice D is incorrect as the essay does not primarily analyze the difference between the SA node and the AV node; instead, it focuses on explaining how an electrocardiograph reads electric currents from the heart.

Correct Answer: A

Rationale: The correct answer is A. Baroreceptors and chemoreceptors send impulses from the arteries, while the kidneys control blood volume. Baroreceptors and chemoreceptors are responsible for monitoring blood pressure by sensing changes in pressure, oxygen levels, carbon dioxide levels, and pH within the arteries. They send out impulses to raise or lower blood pressure accordingly. On the other hand, the kidneys play a crucial role in regulating blood volume by absorbing salts and water and removing waste products. This key difference highlights that while baroreceptors and chemoreceptors are involved in monitoring and regulating blood pressure, the kidneys primarily focus on controlling blood volume. Choice B is incorrect because it inaccurately states that baroreceptors and chemoreceptors help maintain blood volume, which is not their primary function. Choice C is incorrect as it provides an inaccurate comparison between the roles of baroreceptors, chemoreceptors, and the kidneys. Choice D is incorrect as it wrongly associates the location of baroreceptors and chemoreceptors with the adrenal cortex, which is not accurate.

Correct Answer: D

Rationale: In the context provided, 'popular' refers to magazines intended for the general public. The paragraph mentions that Infotrac indexes hundreds of popular magazines and newspapers, including medical journals such as the Journal of the American Medical Association and New England Journal of Medicine. These magazines target a wide audience, making choice D ('for the general public') the correct answer. Choices A, B, and C are incorrect as they do not align with the context of the paragraph.

Correct Answer: A

Rationale: In the context provided, 'deceptive' means misleading. The passage discusses how the Federal Trade Commission (FTC) regulates product advertising to ensure that all information is truthful and not misleading. Therefore, the correct answer is 'A: misleading.' Choice B, 'malicious,' is incorrect as it implies harmful intent, which is not necessarily conveyed by the term 'deceptive' in this context. Choice C, 'illegal,' is incorrect because 'deceptive' does not solely refer to something being against the law, but rather to misleading information. Choice D, 'irritating,' is also incorrect as it does not capture the essence of 'deceptive' as used in the passage.

Correct Answer: A

Rationale: In the context provided, 'sterile' means free of bacteria. The text mentions that raw foods are not sterile and can be a common source of foodborne illnesses due to contamination with harmful bacteria. 'Healthy' (choice B) is incorrect as the term 'sterile' specifically refers to the absence of bacteria, not overall health. 'Delicious' (choice C) is irrelevant to the context of bacteria contamination. 'Impotent' (choice D) is also incorrect as it does not relate to the concept of being free from bacteria.

Correct Answer: D

Rationale: The correct answer is D. The author's primary purpose for writing the essay is to inform the reader about the stages of the water cycle. The essay discusses the various stages of the water cycle, including precipitation, runoff, evaporation, and condensation. Choices A, B, and C are incorrect because the essay focuses on explaining the water cycle stages rather than persuading the reader to conserve water, discussing the effectiveness of runoff, or analyzing different types of runoff.

Correct Answer: C

Rationale: In the context provided, 'pathogens' refers to disease-causing substances such as bacteria and viruses. These microorganisms can contaminate food and lead to foodborne illnesses. Choice A ('diseases') is incorrect as pathogens themselves cause diseases but are not diseases. Choice B ('vaccines') is incorrect as vaccines are used to prevent diseases caused by pathogens. Choice D ('foods') is incorrect as pathogens are not foods, but rather contaminants that can be found in food.

Correct Answer: D

Rationale: The correct steps of the 'wave of excitation' are the excitation of the atrium, excitement of the ventricle, and relaxation of the ventricle. In the described process, the 'wave of excitation' starts with the discharge from the SA node, leading to the excitation of the atrium. Next, the peak ECG corresponds to the excitement of the ventricle, not its relaxation. Finally, the wave concludes with the relaxation of the ventricle, not its contraction. Therefore, choices A, B, and C are incorrect as they do not accurately describe the sequential steps of the 'wave of excitation' as presented in the extract.

Correct Answer: B

Rationale: Sound waves that are farther apart have a lower pitch. The Doppler Effect explains that as objects emitting sound move away, the sound waves become more spaced out, resulting in a lower frequency and a lower pitch. Choice A is incorrect because waves that are closer together have a higher frequency and a higher pitch. Choices C and D are not directly related to determining the pitch of sound waves.