问题
单项选择题
There have been（）medicine in the last 50 years.
A.great advancesin
B.a great advancein
C.great advanceon
D.a great advanceon
答案
参考答案：A
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There have been（）medicine in the last 50 years.
A.great advancesin
B.a great advancein
C.great advanceon
D.a great advanceon
参考答案：A