由that引导的表语从句如：
The trouble is that he misunderstood me.麻烦的是他误解了我 that是不可以省的
有时,引导表语从句的连词that可以省略
The truth is (that) I didn’t finish my term essay. 事实是我没有写完学期论文.
表语从句中应注意：
1. 连接词that一般不能省略,但当主句中含动词do的某种形式时,that可以省略.如：
What I want to do is (that) I can go up to him and thank him. 我想做的事是走到身边去感谢他.
2. 当句子的主语是：advice, demand, decision, desire, idea, insistence, instruction, order, plan, proposal, recommendation, request, requirement, suggestion, wish等名词时,表语从句须用虚拟语气,即：should +do.如：
My advice is that you should go to apologize to him. 我的建议是你应该去向他道歉.