根据《建筑设计防火规范》,乙类火灾危险性的生产场所,厂房耐火等级应是()
A.一级
B.二级
C.三级
D.四级
参考答案:B
------ Sorry, I can’t go camping with you. I have to prepare well enough for the entrance exam.
------_____! We can camp together next time.
A.Don’t say so
B.My pleasure
C.No problem
D.Unless
分别说明建立p坐标系和θ坐标系的物理条件。