50. According to the passage, ________.
(A) auroral activity may sometimes occur at 27-day intervals
(B) the auroras are seen more frequently as the incidence of sunspots decreases
(C) auroras occur closest to the equator only during the periods of solstice
(D) crimson is the dominant color of the auroral displays.

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統計: A(48), B(14), C(7), D(5), E(0) #1566134

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(A) 原文 Since the Sun...
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