肉的腌制过程中亚硝酸盐的作用有（）、（）、（）。

硅肺的特征性病变是（）。

A.类上皮肉芽肿

B.胸膜呈斑状增厚

C.硅肺空洞

D.硅结节

E.肺间质纤维化

一个长方形的篮球场，长是100米，宽是60米．围着这个操场跑两圈，要跑多少米？

-- Let’s see the pandas first.

-- __________.

A．Why do you ask me?

B．That sounds great. Let’s go.

C．What animals do you like?

D．No, I don’t.

— How was your holiday?

— It couldn’t have been _____. I just stayed in the hotel because it was raining most of the time.

A．boring

B．more boring

C．most boring

D．less boring

液氧泵过滤网堵塞应怎么处理？