Question

Scientists say it may be one year or so ________ it is possible to test the new

Scientists say it may be one year or so ________ it is possible to test the new medicine on human patients.
A. when
B. after
C. before
D. since

Answer 1

答案C
词义辨析。句意：科学家们说在有可能把这种新药用于人类前可能需要大约一年的时间。所以选C。