为预防小儿佝偻病,可每日给予维生素D()
A.50U
B.100U
C.200U
D.300U
E.400U
参考答案:E
Have you made up your mind ________ abroad? I advise you to consider it carefully.
A.study
B.to study
C.studying
D.studied
对于球面、抛物面和旋转面的近似展开,一般用()进行。
A.三角形法
B.截面法
C.经线法
D.纬线法