酶促反应中，何种情况下酶反应速度与酶浓度成正比（） A.恒温 B.酶量足够 C.底物

单词拼写。

根据下列各句句意和空白之后的汉语提示词,在指定区域的横线上写出对应单 词的正确、完整形式,每空只写一词.

1. This T-shirt is made of high quality                 (纯的)cotton.

2. More and more Chinese people are able to                (付得起)to travel abroad.

3. The first official results are not expected until                 （星期二)at the earliest.

4. He was wearing a very              (严肃的)expression and I knew something was wrong.

5. Regular tests help the teacher to learn about the                进步)of each student.

6. The open exhibition will allow local                （艺术家)to show their talents.

7. He             (承诺)that he would come,but he hasn11 turned up yet.

8. The staff soon found the new manager easy to           (接近).

9. There is nothing there - you are just              (想象)things!

10. The little girl walked              (自信地)onto the stage, ready for her first speech.

已知一个样本1，2，3，x，5，它的平均数是3，则这个样本的极差是（    ）。

下列变化是通过取代反应来实现的是 （   ）

A．CH₃CH₂OH CH₃CHO

B．CH₂＝CH₂ CH₃－CH₂Br

C．CH₂＝CH₂ +H₂O CH₃CH₂OH

D．

某项目当标准折现率在i_c=10%时，净现值NPV=200万元；当i_c=15%时，净现值NPV=-100万元。用内插公式可求得其内部收益率IRR为( )。

A．11.67%
B．12.5%
C．13.33%
D．15%

客户需求首先源自于对现状的（）。