蒸压粉煤灰多孔砖按强度分为（）三个等级。
A、MU10
B、MU15
C、MU20
D、MU25
参考答案：B, C, D
It's cold outside, but everyone ______ a good time. [ ]
A. has
B. have
C. are having
D. is having
请谈谈你是如何利用多元职能理论分析学生的差异的？
