如何让防止氮气窒息？（）
A、随身携带测氧仪
B、工作时站在上风处
C、检查及堵塞漏氮点
D、氮气危险区加强通风
参考答案：A, B, C, D
小题1:Where will you have classes if you like playing basketball?
A．At Cliff College.
B．At Golden Finger Club.
C．At Whitehawk School
D．At Haved School.小题2:How much will they pay if Darning and his deskmate join “Speak Good English”?
A．$15
B．$30
C．$45
D．$60小题3:All classes will end after _________.
A．1 p.m.
B．2 p.m.
C．3 p.m.
D．4 p.m.
将下列各式分解因式：
（1）3x-12x3
（2）（x2+y2）2-4x2y2．
