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题目内容
（国家开放大学开放英语）
_____, people who don.t smoke are healthier than people who do.
单选题 (2 分) 2分
A.
By average
B.
On average
C.
At average
D.
In average
单选题 (2 分) 2分
A.
By average
B.
On average
C.
At average
D.
In average
参考答案