用所给词的适当形式填空。

     When I first l_____ (eat) in a Western restaurant, I didn't know what I was 2_____ (suppose) to do.

Everything was 3_____ (familiar). I was used to 4_____ (eat) with chopsticks and a spoon, but I had to eat

with a knife, a fork and a spoon. And I 5_____ (have) not just one set to use, but two or three of each.

Questions 6_____ (crowd) my mind. Was I supposed to begin with the 7_____ (large) ones or the 8_____

(small)?

Ames试验最常用的实验方法是（）

A.共培养法

B.预培养法

C.平板掺入法

D.点试法

E.突变法