72里面有几个9?
72÷9=8
On coming into the kitchen, mother found the soiled (污染的) dishes piled _____. [ ]
A. at risk
B. at random
C. at length
D. at ease
有关麻醉用气体储存于压缩气筒内的物理状态,哪项是错误的()
A.氧气呈压缩气状态
B.二氧化碳呈液化气状态
C.空气呈压缩气状态
D.环丙烷呈压缩气状态
E.氧化亚氮呈液化气状态