Which sound waves have a lower pitch?

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.

Correct Answer: A

Rationale: The corrected statement should be: Changes in the ECG are not typically used for the diagnosis of abnormal cardiac rhythm. The passage mentions that the heart sends out electric currents in waves, and the 'wave of excitation' spreads through the heart wall accompanied by electric changes. It details the process of how the heart's electric impulses are recorded and how abnormalities can be detected. However, it does not state that ECG changes are specifically used for diagnosing abnormal cardiac rhythms. Choice A is the correct answer because it misrepresents the information provided in the passage. Choices B, C, and D are all supported by the passage and align with the details mentioned regarding the electrocardiogram and the wave of excitation in the heart.

Correct Answer: B

Rationale: In the context provided, 'emitting' means releasing, specifically referring to the electric currents being released in the body. The passage describes how electric currents are constantly being emitted in the body and can be detected on the body's surface, ultimately recorded by an electrocardiograph. This process is about the release of electric impulses, making 'releasing' the correct interpretation. Choice A, 'Repelling,' implies pushing away, which is not the intended meaning in this context. Choice C, 'Closing,' and Choice D, 'Charging,' do not align with the context of electric currents being emitted.

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: 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.