问题
选择题
Only in 1996 the determination and patience of the scientists with a breakthrough at last .
A.were ; paid off
B.did; pay back
C.did ; pay off
D.did ; pay for
答案
答案:C
Only in 1996 the determination and patience of the scientists with a breakthrough at last .
A.were ; paid off
B.did; pay back
C.did ; pay off
D.did ; pay for
答案:C