letus(缩写形式)__________

“Earlytobed，earlytorise”makesamanhealthy,wealthyandwise.It'sgoodforthebody.Thisisanoldsaying.Haveyouheardofitbefore?Itmeansthatwemustgotobedearlyatnight，andgetupearlyinthemorning.Thenweshallbehealthy.Weshallalsoberichandclever.Thatistrue.Thebodymusthaveenoughsleeptobehealthy.Childrenofyoungageshouldhaveenoughsleep，ortheycan'tdotheirworkverywell.Theywillnotbewiseandtheymaynotbecome。wealthy!.Thebodyalsoneedsexercise:walking,running,jumping,swimming,playinggamesandallother。exercise.Exercisekeepsthebodystrong.Exercisealsohelpsthebloodtomovearoundinsidethe.body.Thisisveryimportant.Ourbloodtakesfoodtoallpartsofourbody.Theheadalsoneeds.blood.Exercisehelpsustothinkbetter.

根据短文内容，回答问题.

1.Whatdoes“earlytobed.earlytorise”mean?

2.Whatmustthebodyhavetobehealthy?

3.WhatwillhappentoChildrenofyoungagewhodon'thaveenoughsleep?

4.Whatkeepsthebodystrong?

5.Whattakesfoodtoallpartsofourbody?

已知阿伏伽德罗常数是NA，铜的摩尔质量为M，铜的密度是ρ，那么以下说法正确的是()

下面相关我国地理差异的叙述，准确的是()

在光滑的水平面上方，有两个磁感应强度大小均为B，方向相反的水平匀强磁场，如图所示PQ两个磁场的边界，磁场范围足够大。一个边长为a、质量为m、电阻为R的金属正方形线框，以速度v垂直磁场方向从如图实线位置开始向右运动，当线框运动到分别有一半面积在两个磁场中时，线框的速度为v/2，则下列说法正确的是