I know Canada.[ ]
A. about
B. in
C. of
答案：A
Can you see the birds _____ the apple tree? They are eating the apples _____ the tree. [ ]
A. in, on
B. at, in
C. at, in
D. on, in
下列哪一项属于三级预防的内容（）
A.普查
B.筛检
C.产前检查
D.康复治疗
E.遗传咨询
