下列不是乳牙作用的是（）
A.有利于恒牙的萌出
B.有利于发音
C.有利于心理健康
D.有利于咀嚼
E.有利于恒牙的发育
参考答案：E
UNIFACE应用开发分成哪3个步骤？
A．建模、应用、装配
B．分析、设计、实现
C．建模、构造、装配
D．建模、设计、实现
—Did Peter fix the computer himself?
—He ____, because he doesn’t know much about computers.
has it fixed B. had fixed it C. had it fixed D. fixed it
