2013年GCT英语日常练习（7.22）
2013-07-22 9:04:17 www.gct-online.com
1.____in the past, at the moment it is a favorite choice for wedding gown.
A. Unpopular has as white been
B. White has been as unpopular
C. Unpopular has been as white
D. Unpopular as white has been
2.____for a long time, the fields are all dried up.
A. There has been no rain
B. Having no rain
C. There having been no rain
D. There being no rain
3. The millions of calculations involved, ____by hand, would have lost all practical value by the time they were finished.
A. had they been done
B. they had been done
C. having been done
D. they were done
4. Televisions enable us to see things happen almost at the exact moment____.
A. which they are happening
B. they are happening
C. which they happen
D. they have happened
5.____me most was that the young boy who had lost both arms in an accident could handle a pen with his feet.
A. That amazed B. It amazed C. Which amazed D. What amazed
6. Although she wrote a lot of short stories and poems when she was very young, ____she was twentyfive.
A. her first real success did not come until
B. her real first success came until not
C. since her first real success did not come until
D. not until her first real success
7. You should know better than____ your little sister at home by herself.
A. to leave B. leaving C. to have left D. left
8. As the train will not leave until one hour later, we ____grab a bite at the snack bar.
A. may well B. just as well C. might as well D. as well
9. She resorted to ____ when she had no money to buy foods for her children.
A. have stolen B. steal C. stole D. stealing
10. The boy has admitted to ____ the window while playing football yesterday.
A. breaking B. having been broken C. break D.be breaking
(本期答案明日公布)
【7月20日答案与解析】
1.将2X-Y看作一个随机变量，则
E(2X-Y)2=D(2X-Y)+[E(2X-Y)]2
=4DX+DY+(2EX-EY)2
=4×2.1+2.4+(2×3-4)2
=14.8
2.根据题意，设甲水库中的存水量为6a，则乙水库中的存水量为3a，甲、乙两水库中的存水总量是9a。
两座水库的水量相等，即甲、乙两水库都有(3a+6a)÷2=4.5a，也就是说，甲水库需要向乙水库输出的水量是(6a-4.5a)=1.5a。
那么，甲水库向乙水库的输水量占其存水量的比为：1.5a÷6a=25%
故本题答案为B。
3.根据题意，设甲单独做完整个工程需要x天，乙单独做完整个工程需要y天，则
x+y=22
x/30+y/20=1
解之，得x=6
y=16
故本题应该选B答案。
4.(a+2b)÷(2a-b)=2
a+2b=2(2a-b)
a+2b=4a-2b
4b=3a
a/b=4/3
故本题答案为C。
5.根据题意，设该公司优秀员工为x人，则非优秀员工为(50-x)人，那么
90x+75(50-x)=50×81
则，x=20
故本题答案为B项。
6.这道题可以用代入法求解。假设n=1，则n的15倍除以10的余数是5，A项可排除;假设n=3，则n的15倍除以10的余数是5，B项可排除;假设n=5，则n的15倍除以10的余数是5，C项可排除;假设n=6，则n的15倍除以10没有余数，符合题意，D项为正确答案。
7.(3a2-5ab+2b2)÷(2a2+3ab-5b2)=[(a-b)(3a-2b)]÷[(a-b)(2a+5b)]=(3a-2b)÷(2a+5b)
因为a/b=3/4，
那么a=3b/4，
那么(3a-2b)÷(2a+5b)=(9b/4-2b)÷(6b/4+5b)=b/4÷26b/4=1/26
