求解 三个个问题， 大牛们帮忙！

beingchuang

1. In the last few years, the number of convinced criminals given community sentence, which allows the criminals to remain unconfined while they performing specific jobs benefitting the public have risen dramatically.
A.sentence, which allows the criminals to remain unconfined while they performing specific jobs benefitting the public have risen dramatically.
B. sentence, performing specific jobs benefitting the public while remain unconfined, have risen dramatically.
C. sentence, performing specific jobs benefitting the public while they are allowed remain unconfined, have risen dramatically.
D. sentence which allowed them to remain unconfined in their performing of specific jobs beneficial to the public has
E. sentence allowing them to remain unconfined while performing specific jobs that are beneficial to public, has
答案选E，可是E 有歧义啊， 这里performing specific jobs 也可以修饰sentence,这肯定不对吧？
另外就是：
14. A recent study of the public school shows that there are now one computer for every 23 students, 4 times as many than there were four years ago.
A. there are now one computer for every 23 students, 4 times as many than there were
B. there is now one computer for every 23 students, 4 times as many than there were
C. there is now one computer for every 23 students, 4 times as many as there were
D. every 23 students now has a computer, 4 times as many as there were
E. every 23 students now have a computer, 4 times as many than there were
答案选C，可是为什么前面用IS 后面用WERE啊？
15. Although the Supreme Court ruled as long ago as 1880 that blacks could not be excluded from outright jury services, nearly a century of case by case adjudication has been necessary to develop and enforce the principle that all juries must be drawn from “a fair cross session of the community”
A.nearly a century of case by case adjudication has been necessary to develop and enforce the principle that all juries must be
B. was necessary for developing and reinforcing the principle of all juries being
C. was to be necessary in developing and reinforcing the principle of all juries to be
D. is necessary to develop and reinforce the principle that all juries must be
E .will be necessary to develop and reinforce the principle of all juries being
答案选A，但是，necessary也可以用完成时态吗？

谢谢大家不惜赐教！

bitieming

第三题develop和enforce都是一个过程，为了表达“自从1880年的rules以来一直在develop和enforce，而这个进程中case也'一直以来很重要'”的意思，完成时是需要的~

bitieming

第二题解释无能…虽然想说考点不在这……但是的确不明白……

bitieming

第一题allowing修饰的就是community sentence，allowing后面就是对这种判罚（社区服刑）的解释~

beingchuang

难道就没有人回答我了？

beingchuang

大家帮帮我啊！！！