我国陆上国界线长达______多千米,接壤的国家有______个。
2万(20000);14
如图所示是一列简谐波在某一时刻的波形,则在该时刻( )
A.B、C两点相距λ4,即1m
B.B点的振幅最大,C点的振幅是0
C.经一个周期,质点从A点到达E点
D.如果质点B在0.35s内通过的路程为14cm,则波速为20m/s
There would be not a good harvest of wheat in North China this year()the big snow.
A. in spite of
B. apart from
C. due to
D. in case of