以下有关酶偶联法测定酶活性浓度的描述，错误的是A．往往利用一个以上的工具酶 B．测定

简述舌 * * 的种类及功能。

孕妇血容量增加达高峰的时间是（）。

A.孕12～19周

B.孕20～28周

C.孕28～30周

D.孕32～34周

E.孕36～38周

观察下面的路线图，填入恰当的单词完成图后的对话，每空一词。

A: Hello! Is there a bank __1__ here?

B: Yes, there is. But it's a little far __2__ here.

A: Can you tell me how to __3__ to the bank?

B: Sure. Go down this street, and walk across the __4__ over the river. Then turn __5__ on

    Zhongshan Road. Go __6__ and turn left at the second turning (转弯处). Then you can __7__ it.

    It's next to the  __8__.

A: Thanks very much.

Some students were late for class because they had been _________ by the heavy storm.

A．kept

B．stopped

C．slowed

D．delayed

线性码的封闭性就是任意两个许用码组按位（）后得到的新码组任为一（）码组。