设备材料采购合同的订立方式有( )。
A．公开招标
B．邀请招标
C．直接订购
D．间接订购
E．询价
参考答案：A,B,C,E
To have a dinner at a restaurant on the Eve of the Spring Festival, you need to reserve the
restaurant months before, _____? [ ]
A. mustn't you
B. didn't you
C. don't you
D. needn't you
气相色谱的检测器如何分类？
