2. Is               necessary to tell his father everything ?

     A. it         B. that            C. what         D. he

〖答案与简析〗选A。测试 it 用作形式主语，代替由不定式（或不定式复合结构）、动名词或从句表示的真正主语。又如：

1）Is               possible to fly to the moon in a spaceship ?

     A. now            B. man           C. that            D. it

2）Is               necessary to complete the design before National Day ?

     A. this             B. that            C. he              D. it

3）Does           matter if he can't finish the job on time ?

     A. this             B. that            C. he              D. it

4）It worried a bit          her hair was turning grey .

     A. while          B. that            C. if D. for

答案1） ―  4）DDDB。