硫化氢的主要物、化特性有（）。
A.无色剧毒
B.强酸性气体
C.比空气重
D.对钢材有腐蚀性
E.燃烧后无毒性
参考答案：A, B, C, D, E
It was not until she got home _______ Jennifer realized she had lost her keys. [ ]
A. when
B. that
C. where
D. before
