古代人常利用银与砷的化学反应来检验食物中是否有()。 发布时间:2017-11-19 23:33 │ 来源:www.tikuol.com 题型:填空题 问题: 古代人常利用银与砷的化学反应来检验食物中是否有()。
题型:填空题 Everyone knows _____ is dangerous to play with fire, but _____ is difficult is to prevent children from playing with fire. [ ]A. that; it B. it; it C. that; what D. it; what 查看答案