—How old are you?
—I'm fifteen. I was born _______ 1990. [ ]
A. in
B. at
C. on
D. for
答案:A
轴承内圈与轴的配合通常采用基孔制配合。
常吃海带、紫菜等含碘丰富的海产品可以防治
A.侏儒症
B.大脖子病
C.巨人症
D.糖尿病