精选优质文档-倾情为你奉上（英语）高中英语现在完成时练习题一、单项选择现在完成时1 When will the bike-sharing schemes be introduced to the public? Not until _ a better understanding of them.Awe have had Bwill we have hadChave we had Dwe will have had【答案】A【解析】【详解】考查时间状语从句。句意：-公共单车共乘计划将于何时推出?-直到对它们有了更好的了解。根据第一句话可知这是将来时，但是until引导的是时间状语从句，从句中要用现在时代替将来时。not until位于句首时，主句要用部分倒装，但是从句不用，故选A。2Tom _on the essay for two hours but he _only a hundred words by now.Ahas been working;has w
