带电粒子以速度v沿CB方向射入一横截面为正方形的区域.C、B均为该正方形两边的中点,如图所示,不计粒子的重力.当区域内有竖直方向的匀强电场E时,粒子从A点飞出,所用时间为t1;当区域内有垂直于纸面向里的磁感应强度为B的匀强磁场时,粒子也从A点飞出,所用时间为t2,下列说法正确的是( )
As an engineer, you can't be careful. You should pay attention to every detail.( )
A.veryB.tooC.soD.quite
We must find out the professor is coming, so we can book a room for him.( )
A.howB.whyC.whenD.where
I look stupid with this haircut. All my classmates will me.( )
A.laugh atB.agree with
C.depend onD.worry about
Sandy seemed this morning. Do you know what was wrong?( )
A.satisfiedB.relaxedC.amazedD.unhappy
Millie spoke in a very low voice, but I understand what she said.( )
A.couldB.mightC.canD.may