Q24:

A March 2000 Census Bureau survey showed that Mexico accounted for more than a quarter of all foreign-born residents of the United States, the largest share for any country to contribute since 1890, when about 30 percent of the country’s foreign-born population was from Germany.

1. the largest share for any country to contribute

2. the largest share that any country has contributed

3. which makes it the largest share for any country to contribute

4. having the largest share to be contributed by any country

   e,having the largest share to have been contributed by any country

不太明白a为什么不对,答案是选b