____ ____ great book it is !
国家统一是中国历史发展的主流。公元6世纪80年代,使中国重归统一时的皇帝是( )
—That's good to environment. We can also learn from ancient people.
在一均匀介质中选取平衡位置在同一直线上的9个质点,相邻两质点间的距离均为0.1m,如图甲所示。一列横波沿该直线向右传播,t=0时到达质点1,质点1开始向下运动,振幅为0.2m,经过时间0.3s第一次出现如图乙所示的波形。则( )
— In addition, you and I have lots of things in common.
— I really can't agree more.