常用的混凝土振动器类型有：__________振动器、__________振动器、表面振动器、振动台。
参考答案：内部，外部
-Julia Morgan, the famous movie star, plans _________ a relaxing vacation
in Spain.
-I hope he will have a good time.[ ]
A. having
B. has
C. to have
D. have
卫生经济学
_______ a relaxing vacation