根据下表中列出的几种常见的气体和空气的性质,可知其中既能用排水法又能用向下排空气法收集的是
A.甲烷
B.二氧化硫
C.氨气
D.氯化氢
答案:A
She has been giving ________ a parttime job to support her poor family.[ ]
A. a thought to taking
B. a thought to take
C. thought to taking
D. thought to take
资源供求关系情况由公司在下达()文件时予以明确。