unknown 请教几道语法题

zulo_zl

新东方TOEFL 全真试题20套

Test1---40题

To reach (a target) of (spending) a billion dollars (in a ) lifetime, a human being would have to spend money (at rate) of more than 50,000 dollars per day.

为何选d 少了a吗？

Test---16题

（As the) US border (pushed) further west, the MId-west territories (developd) economically and industrially and big cities (such) as Chicago,St.Louis and Cincinnati-appeared.

B错了是因为应该用被动吗？

Test2---19题

The number (of) seats in the Senate (has) always equal to twce the number of states,(thus) there are two senators (for) every state.

has应该改问have 吗？ 不是应该用单数吗

谢谢~~~