it is a serious problem.we can't decide ____ Mr Harris comes back.

分类: 作业答案 • 2022-01-14 11:35:41

问题描述：

it is a serious problem.we can't decide ____ Mr Harris comes back.
a.while b.since c.until d.so
选哪个~解释下~

答

这句只能用not...until句型,所以选C.其他三项都不与not连用.