对于稳定的晶体结构，可能存在的配位数有（）个。
A.4
B.6
C.7
D.8
参考答案：B
Being exposed for a long time _____ strong sunlight might seriously damage your skin. [ ]
A. in
B. under
C. to
D. over
关于甲类、乙类易燃易爆物品的厂房、库房与防空地下室的防护距离,以下哪项正确?
A.60m
B.50m
C.40m
D.30m
