广告调查的特点()
A.目标明确
B.操作性强
C.操作性差
D.保密性强
E.具有累积性
参考答案:A, B, D, E
Many people like white color as it is a ________ of purity.
A.symbol
B.sign
C.signal
D.example
齿轮泵有哪些主要零件()
A.轴承
B.泵体
C.端盖
D.齿轮