C70采用屈服极限为（）的高强度钢新型中梁。
A.420MPa
B.450MPa
C.460MPa
参考答案：B
He found it hard to express his his brother's success. [ ]
A．envy on
B．envy to
C．envy of
D．envy toward
消防证下次复审期限为几年？
