通风机的水柱计及轴承温度计，应（）校验一次。
A、每季
B、每半年
C、每年
D、每两年
参考答案：C
Shelly had prepared carefully for her biology examination so that she could be sure of
passing it on her first ____. [ ]
A. attraction
B. attempt
C. arrival
D. article
设计分离面
