36.  The ash from a volcano spreads worldwide in a few days and remains in the air for years. Its effect is to turn incoming solar radiation into space and however cool the earth.
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【正确答案】 1、D。根据上下文的逻辑关系，此处表达的是因果关系，而非转折关系。因此，however应改为thus。    
【答案解析】