水处理设备的混凝土基础应达到承重强度的（）以上时再安装。
A.70%
B.75%
C.80%
D.85%
参考答案：B
—Have you washed your clothes yet?
—They________ now.[ ]
A. has washed
B. is washed
C. are being washed
D. is washing
库血保存时间不超过( )
A．3天
B．1周
C．3周
D．4周
E．5周
