the meeting himself gave them a great deal of encouragement. A.The president will attend B.The president to attend C.The president attended D.The president’s attendin
如图所示，一小球套在光滑轻杆上，绕着竖直轴OO′匀速转动，下列关于小球受力的说法中正确的是（ ）
补写下列名句中空缺部分 ①君子坦荡荡， 。 ② ， ，颁白者不负戴于道路矣。（《王好战，请以战喻》
I the saxophone at regular intervals for many years when I was a child． A．played B．was playing C．has played
已知＝（2,1）, ＝10, ＝,则＝ （ ） A． B． C．5 D．25
—Who’s the little baby in the photo, Li Ying? —It’s me. This photo _______ fourteen years ago. A. is taken B. took C. takes D. was taken
1 won’t call you, ________ something unexpected happens. A. unless B. whether C. because D. while
均匀带电的球壳在球外空间产生的电场等效于电荷集中于球心处产生的电场．如图所示，在半球面AB上均匀分布正电荷，总电荷量为q，球面半径为R，CD
,求m、n. 
［t+(m-n-4)+
］=0