31．(2015·湖南高考)Always ________ in mind that your main task is to get this company running smoothly.
A．to keep B．to have kept
C．keep D．have kept
解析：选C 考查祈使句。句意：一直要记住：你的主要任务是使这家公司运转顺利。祈使句一般以动词原形开头，故用keep。
23．(2015·湖南高考)Only after talking to two students ________ that having strong motivation is one of the biggest factors in reaching goals.
A．I did discover B．did I discover
C．I discovered D．discovered I
解析：选B 考查部分倒装。句意：直到跟两个学生谈了话以后，我才发现有强烈的动机是达到目标的最重要的因素之一。only修饰after引导的时间状语，且位于句首，故句子需用部分倒装语序。
21．(2015·湖南高考)It was when we were returning home ________ I realized what a good feeling it was to have helped someone in trouble.
A．which B．that
C．where D．how
解析：选B 考查强调句型。句意：是我们快要回家的时候，我才意识到了帮助有困难的人感觉多么美妙！强调句型的基本结构为“It is/was＋被强调部分＋that/who＋剩余部分．”。若将It is/was与that/who去掉，句子成分仍然完整，那么该句就是强调句。
