选词填空。

(what, who, where, how  many, what's)

1.-        is my father? -He's in the study.

2.-        is she? -She's my sister.

3.-        this in English? -It's a copybook.

4.-        birds can you see? -I can see five birds.

5.-        time is it? -It's six o'clock.

足球赛的票价为每张80美元时，某人打算买两张，但票价涨到每张100美元时，他决定在家看电视转播。求足球赛票的需求弹性。