当空气中氧气浓度小于()%时,人呼吸困难,心跳加快。A.17 B.15 C.12 D 发布时间:2019-12-05 05:47 │ 来源:www.tikuol.com 题型:单项选择题 问题: 当空气中氧气浓度小于()%时,人呼吸困难,心跳加快。A.17B.15C.12D.3
题型:单项选择题 All the money he had was ______, so he had to make a living by begging.[ ]A. used up B. taken upC. stayed up D. brought up 查看答案