Question

【题目】The waste water has been made clean before it goes into the river ________ the new rule was made.

A. whenB. ever sinceC. after D. before

Answer 1

【答案】B

【解析】

试题分析：考查连词。when当……时；ever since自从；after在……之后；before在……之前；句意：自从新规则被制定以来，在废水进入河流之前，就已经被处理干净了。主句中使用现在完成时，说明应该使用ever since引导这个时间状语从句。故B正确。