Scientists say it may be five or ten yea
题型:选择题
问题:
Scientists say it may be five or ten years___________ it is possible to test this medicine on human patients.
A.since
B.before
C.after
D.when
Scientists say it may be five or ten years___________ it is possible to test this medicine on human patients.
A.since
B.before
C.after
D.when