Question

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

Answer 1

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。