企源知识库

The day will come _____ coal and oil will be used as raw material rather than fuels.
A、as
B、while
C、when
D、whether
【正确答案】：C
【题目解析】：as意为”正如“；while意为”然而“；when意为”当...时“；whether意为”是否“。句意：总有一天煤和石油将被用作原料而不是燃料。