What is the best summary of the passage?

Correct Answer: C

Rationale: The correct summary of the passage is option C. The passage explains how the ECG systematically measures and records the 'wave of excitation' that occurs within the heart in three distinct steps, spreading from the SA node to the AV node. This summary effectively captures the main focus of the passage. Option A is incorrect because it only mentions the detection of electric currents in the body and recognizing abnormalities by medical staff, missing the key information about the 'wave of excitation' and its stages. Option B is incorrect as it focuses solely on the measurement and recording of unique electric currents on the body's surface, neglecting the specific process described in the passage. Option D is also incorrect as it provides a general description of how the ECG measures electric currents without emphasizing the specific stages of the 'wave of excitation' as detailed in the passage.

Correct Answer: B

Rationale: In the context of the given extract, 'evolved' means to gradually develop. The systems in the body have evolved over time, indicating a gradual development and adaptation. 'To spread,' 'to revolve,' and 'to shift' do not capture the idea of a gradual development as portrayed in the text, making them incorrect choices.

Correct Answer: C

Rationale: The primary purpose of the essay is to inform the reader about how the cardiovascular system regulates blood pressure. The essay provides detailed explanations about the components of the cardiovascular system that regulate blood pressure, such as baroreceptors, chemoreceptors, and the kidneys. Choices A and B are incorrect because the essay does not focus on discussing the dangers of high blood pressure or its correlation with a higher risk of heart attack. Choice D is incorrect as the essay does not aim to persuade the reader to control their blood pressure but rather to educate them on the regulatory mechanisms of the cardiovascular system.

Correct Answer: B

Rationale: The correct answer is B because it provides a comprehensive summary of the passage, explaining how the cardiovascular system regulates blood pressure through baroreceptors, chemoreceptors, and the kidneys. Choice A is incorrect as it only focuses on the heart and kidneys without mentioning the broader cardiovascular system. Choice C is incorrect as it solely emphasizes the role of baroreceptors in regulating blood pressure. Choice D is incorrect as it oversimplifies the role of chemoreceptors in monitoring oxygen levels without mentioning their impact on blood pressure regulation.

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.