下列基质中,不能作栓剂基质的是 ( )
A. 甘油明胶
B. 聚乙二醇
C. 凡士林
D. 可可豆酯
E. 半合成棕桐油酯
Nowhere ______ so many people planting trees.
A. have we seen
B. we have seen
C. have seen we
D. we saw
我患有漫游癖,只有在闲逛旅游时,我才感到愉快。
A. 是
B. 否
Scientists ______that bacteria through microscopes for many years.
A. studied
B. have studied
C. had studied
D. have seen studied