用不定冠词a或an填空。

1．Maths is ________ useful subject．You can't drop it, I think．

2．It is ________ long time since we met last．

3．Tom's father is ________ artist and his mother is ________ engineer．

4．Last Sunday we had ________ good time．

5．There are only two letters in the word“us”, ________“u”and ________“s”．

6．Before he became ________ university student, he was ________ army man．

7．I spent ________ hour and ________ half writing the composition．

8．Do you have ________ answer to my question?

9．Have you got ________ ten-yuan note?

10．The car has ________ ugly colour．