在1秒内通过一定点的完整波形的个数叫做波长。()
参考答案:错
甲书的页数是乙书的4倍,甲乙两书共损坏16页之后,未遭损坏的页数之和是489页,问甲书共有多少页( )
A.365
B.387
C.396
D.404
I don't know __ _.[ ]
A. how to do that
B. how do that
C. how do you do that