Walking down a path through some woods in Georgia, I saw a water puddle (水坑) ahead on the path. I changed my direction to __1__ it on the part of the path that wasn’t covered by water and mud. __2__ I reached the puddle, I was suddenly attacked! But I was __3_. After all, I was being attacked by a butterfly! I took a step forward. My attacker __4__ me again. He pushed and struck me __5__ with his head and body, striking me over and over again with all his might. For a second time, I moved back a step __6__ my attacker gave up his attack. Yet again, I tried moving __7__, my attacker charg
如图所示,M、N是正点电荷产生的电场中的一条电场线.一个电子从a到b穿越这条电场线的轨迹如图所示.关于该电子在a、b两点的加速度和速度大小的说法正确的是( ) A.aa>ab va>vb B.aa>ab va<vb C.aa<ab va>vb D.aa<ab va<vb