The strangest weather of last year was possibly not on Earth, but on the Sun. Every 11 years【C1】______the Sun goes through a cyc

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问题     The strangest weather of last year was possibly not on Earth, but on the Sun. Every 11 years【C1】______the Sun goes through a cycle of sunspots—actually magnetic storms erupting across its surface. The number of sunspots【C2】______its minimum in 2007 and【C3】______have increased soon afterwards, but the Sun has remained strangely quiet since then. Scientists have been baffled as weeks and sometimes months have gone by without a single sunspot, in【C4】______is thought to be the deepest solar minimum for almost 100 years.
    This【C5】______of solar activity means that cosmic rays reaching Earth from space have increased and the planet’s ionosphere in the upper atmosphere has sunk in【C6】______, giving less drag on satellites and making collisions between them and space junk more likely. The solar minimum could also be cooling the climate on Earth because of slightly diminished solar irradiance. In fact, the quiet spell on the Sun may be【C7】______some of the warming effects of greenhouse gases, accounts for the somewhat flat temperature trend of the past decade. But【C8】______if this solar minimum is offsetting global warming, scientists stress that the overall effect is relatively slight and certainly will not last.
    The Sun has gone into long quiet spells before. From 1645 to 1715 few sunspots were seen during a period called the Little Ice Age, when short summers and savage winters often plagued Northern Europe. Scotland was hit particularly【C9】______as harvests were ruined in cold, miserable summers, which led to famine, death, migration and huge depopulation. But whether the quiet Sun was entirely to blame for it remains highly【C10】______.
【C4】

选项 A、which
B、that
C、what
D、how

答案C

解析 整个句子的意思是:科学家们一直迷惑不解的是数周、有时候甚至数月过去了,却没有一个太阳黑子出现。——被视为是近100年来太阳活动极小期。根据句子大意以及介词in推理,此处要一个关系代词引导的宾语从句,且这个关系代词在宾语从句中做主语,指代上一句所说的“数周、有时候甚至数月过去了,却没有一个太阳黑子出现”。分析各个选项,选出符合文意的项。A项which“哪一个”可以做关系代词,引导宾语从句,但是必须和名词结合;B项that“那个”可以做关系代词,引导宾语从句,但是与in结合表示“因为”,与此处句意不符;C项what“什么”可以引导宾语从句,并在宾语从句中做主语,表示以上所说的一切;D项how“怎么样”是关系副词。文中所要表达的是“这一现象(数周、有时候甚至数月过去了,却没有一个太阳黑子出现)被视为是近100年来太阳活动极小期”,所以选择C。
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