进出口许可证的有效期一般为( )。
A.6个月
B.12个月
C.18个月
D.24个月
参考答案:D
It was rainy all day. We had to stay _____ home. [ ]
A. at
B. in
C. from
D. around
未角化复层鳞状上皮细胞分布在下列哪个器官?()
A.食管
B.气管
C.输卵管
D.输精管
E.输尿管