补全对话

A: Excuse me. Can you tell me the   _1_   to the post office?

B: Of course. It's  _ 2_   here. Go to the corner and  _ 3 _ left. The post office is   _4_   the end of the street. You can't   _5   it.

A: Thank you very much. I'm   _6   I'll find it.

B:   7_   is one important thing I   _8   to tell you.

A:   __9_   that?

B: Today is a holiday. The post office is   _10_  .

1.______ 2.______ 3.______ 4.______  5.______

6.______ 7.______ 8.______ 9.______ 10.______

蛋白质空间构象的特征主要取决于下列哪一项（）

A、多肽链中氨基酸的排列顺序

B、次级键

C、链内及链间的二硫键

D、温度及pH