《混凝土结构设计规范》规定，钢筋混凝土结构的混凝土强度等级不应低于( )。
A．C15B．C30C．C40D．C60
参考答案：A
The woman looked ______ at her hungry children but didn't know where to get any food. [ ]
A. sad
B. sadly
C. worried
D. angrily
(1234+2341+3412+4123)÷(1+2+3+4)=
A．1003
B．2000
C．1111
D．1000
