Illegal aliens are people living in the U.S.A with proper__1__
authorization. Many entered the country by sneaking
across the border. Others came on temporary student or
visitor visas and did not leave until their visas were expired.__2__
Most illegal aliens want to stay in the U.S.A. because
employment opportunities are so much great than in
their native country. Since illegal aliens try hard not to
be discovered by the government, it is possible to get an __3__
accurate count of them. Recent estimates ranged from __4__
2.5 million to as high as 12 million. In 1986, the United
States government adopted a new law affected illegal aliens— __5__
the Immigration Refrom and Control Act. This law
was designed to accomplish two main goals:1) to allow
illegal aliens who have been living in the country since __6__
January, 1982 to gain legal status if they applied by May 4,
1988; and 2) to encourage others from coming into or __7__
staying in the country illegally by making difficult for__8__
undocumented people to find employment. The law
prohibits American employers from hiring illegals and
providing for severe penalties—fines and even imprisonment—__9__
if they do so. This new law has helped large number of__10__
formerly illegal aliens to become legal residents. But it also
forces employers to check on all prospective employees who
look or sound foreign to be sure that they have documents
allowing them to work. This may discourage some employers
from hiring any immigrants.

答案及解析：
1. with—without
根据illegal aliens的定义，应该是people living in the U.S.A without proper authorization

2. until—when
从逻辑意义上来分析，是Others....did not leave when their visas were expired（当签证到期时他们也不离开美国）

3. possible—impossible
从上下文的说明判断，要弄清楚到底有多少非法居住在美国的外国人，或得一个确切的数据是完全不可能的

4. ranged之前加have
因为是指did not leave until their visas were expired. Recent estimates而不是以往的estimates

5. affected—affecting
此处相当于（a new law）which/that affect illegal aliens

6. have—had
用过去完成时，因为整个句子讨论的是过去的事，并且此处具体指country since
January, 1982 to gain legal status if they applied by May 4,1988

7. encourage—discourage
如果为encourage则与全文的逻辑和意义矛盾

8. 在difficult之前加it
making it difficult for undocumented people to find employment，其中it为形式宾语，实际宾语为不定式短语（for undocumented people）to find employment

9. providing—provides
provides for severe penalties与prohibits American employers from hiring illegals 为并列谓语，而不是与hiring illegals并列

10. number—numbers或在large之前加a
习惯为numbers of或a number of