Scientists say it may be five years ____
题型:选择题
问题:
Scientists say it may be five years _____ it is possible to test this medicine on human patients.[ ]
A. since
B. until
C. before
D. when
Scientists say it may be five years _____ it is possible to test this medicine on human patients.[ ]
A. since
B. until
C. before
D. when