句型练习。

1. The shirt cost me only 50 yuan.   （就划线部分提问）

                                       did the shirt cost?

2. That dictionary cost me $10 . (同义句)

I                    10                    for that dictionary. 

3. My parents should allow me to study with friends.（改为被动句）

I should                                     to study with friends.

4. I used to be a naughty boy. (改成一般疑问句)

              you                              be a naughty boy?

5. The little boy cried because he was hungry.（就画线部分提问）

                                     the little boy cry?

再DNA复制时插入一对碱基，会引起三联体密码（）

A、替换

B、倒位

C、移码

D、缺失