问题
选择题
Scientists are warning that ________ emissions of carbon (碳排放) are cut, we could be heading for an environmental disaster.
A.before
B.as
C.unless
D.in case
答案
答案:C
C 考察连词。Before在…之前;as因为,由于;unless除非,如果不;in case万一,假使;句义:科学家警告说如果碳排放不下降,我们会面临环境灾难。根据句义和逻辑关系可知C正确。