甲烷是无色、微有葱味的气体,难溶于水。当空气中甲烷浓度高达多少时才有毒性?() A. 发布时间:2018-11-03 03:36 │ 来源:www.tikuol.com 题型:单项选择题 问题: 甲烷是无色、微有葱味的气体,难溶于水。当空气中甲烷浓度高达多少时才有毒性?()A.25-30%B.80%C.90%D.10%
题型:单项选择题 Such poets as Shakespeare _____ widely read, of whose works, however, some _____ difficult to understand. [ ]A. are; are B. is; isC. are; is D. is; are 查看答案