锅炉附属件按用途分类有哪几种？
参考答案：
锅炉附件是：水表、汽压表、安全阀、放水阀、注水器、锅炉止回阀、调节阀、送风器。
— Has Li Hong gone to the library?
— Pardon?
— I asked the library.
A．if Li Hong had gone to
B．if had Li Hong gone to
C．Li Hong had gone to
D．has Li Hong gone to
商品的定期检查中，一般在温暖潮湿季节至少（）检查一次。
A、每周
B、每半月
C、每月
D、每10天
