学前期是儿童语言获得的（）时期。
参考答案：关键
Chinese athletes did a great job in the Winter Olympics in Canada. It can encourage post－90s(90后) .[ ]
A. work harder
B. worked harder
C. working harder
D. to work harder
A320飞机（2343-2352）的发动机型号为（）
A、V2500
B、GE90
C、CFM56-3
D、ERJ
