8.　　 --Be careful! Don’t forget you are on a ladder.

--But you are holding it for me, nothing ______________.

7.　　　 Gun control is a subject 　　　Americans have argued for a long time. 　

6.　　 It suddenly _________ to me that we could use the computer to do the job.

5.　　 It snowed heavily for three days _________ and we were separated from the outside world.

4.　　 What disappointed us was that their determination finally_________.

3. It’s quite _______ me why such things have been allowed to happen.

2．Let’s learn to use the problem we are facing _____ a stepping stone to future success.

第一节 单项填空 (共20小题；每小题0.5分，满分10分)

1. Many people have come to realize that they should go on　　 _ balanced diet and make　 ____ room in their day for exercise.

21. 已知条件p：|5x－1|>a和条件，请选取适当的实数a的值，分别利用所给的两个条件作为A、B构造命题：“若A则B”，并使得构造的原命题为真命题，而其逆命题为假命题.则这样的一个原命题可以是什么？并说明为什么这一命题是符合要求的命题.

20．对1个单位质量的含污物体进行清洗，清洗前其清洁度(含污物体的清洁度定义为：

1－)为0.8，要求洗完后的清洁度是0.99．有两种方案可供选择，方案甲：一次清洗；方案乙：两次清洗．该物体初次清洗后受残留水等因素影响，其质量变为a(1≤a≤3)．设用x单位质量的水初次清洗后的清洁度是(x＞a－1)，用y质量的水第二次清洗后的清洁度是，其中c (0.8＜c＜0.99)是该物体初次清洗后的清洁度．

(1) 分别求出方案甲以及c＝0.95时方案乙的用水量，并比较哪一种方案用水量较少；

(2) 若采用方案乙，当a为某定值时，如何安排初次与第二次清洗的用水量，使总用水量最少？并讨论a取不同数值对最少总用水量多少的影响．