The scientists form ( ) United States live on ( )eighth floor of the building .
问题描述：
The scientists form ( ) United States live on ( )eighth floor of the building .
A.the an B.an the C.the the D.an an
I found ( )not very difficult to solve the problem.
A.that B.it C.myself D.this
题没抄错啊
答
C USA前面必须要定冠词the,序数词前面也要the
B it 形式宾语