1 . ____________is illegal to sell cigarettes to children who are under age.

2 . ________ felt funny watching myself on TV. (用适当的词填空)

3 . It takes him one hour _______ (play) sports every day. (所给词的适当形式填空)

4 . ________ will be quite difficult to get used to all the homework. Still, I’m happy to be here. （用适当的词填空）

5 . ________ is known to all that the earth goes around the sun. （用适当的词填空）

6 . ______ is necessary for us teenagers to learn something about ancient Chinese literature. (用适当的词填空)

7 . ________ was his duty to attend to this matter.(用适当的词填空)

8 . ________ is my fault to ask you to add such a plain plot to this perfect story.(用适当的词填空)

9 . ________ is certain that the computer has deeply changed our lives and our ________(social). (所给词的适当形式填空)

10 . ________ is advisable to keep a little food in reserve in case ________ emergency.(用适当的词填空)