为保证压滤机的过滤效果要求清洗一次滤布（）
A、每班
B、每天
C、每3天
D、每星期
参考答案：B
—How do you find your new classmates?
—Most of them are kind. But _________ is so good to me as Bruce.
A．none
B．no one
C．every one
D．some one
止水带的种类和用途有哪些
