物业服务定价成本监审应当遵循的原则有()等。
A.有效性
B.合法性
C.及时性
D.对应性
E.合理性
参考答案：B, D, E
-Maths is too hard for me. Mum, I failed again.
-Come on, dear. __________ is difficult in the world.[ ]
A. Everything
B. Something
C. Anything
D. Nothing
