5.   It + be + time +  that-clause

这个句型属虚拟语气结构，不管主句中用的是 is 或 was ，that从句都须用动词的过去式或should + 动词原型(但不及用过去式普通)，在time之前有时可加上high或about 以加强语气。例如：

 It is time(that)we handed in our exercises .(= It is time that we should hand in our exercises .)

It is high time  (that ) she wrote a letter to her boyfriend .