铝合金大气腐蚀相对湿度大约为（）
A、90%
B、100%
C、65%
D、20%
参考答案：C
23. It's reported that at least one Chinese vessel________in the hands of attackers in Somalia so far.
A．had been
B．has been
C．was
D．Is
吊环式开门单轮滑车最常见的故障是什么？应采取何种对策？
