A:3
B:2
C:6
D:3
It's hard to believe _____ the way out of the forest without the help of the local guide?
一带正电的粒子仅在电场力作用下从A点经B、C运动到D点,其“速度—时间”图象如图所示。分析图象后,下列说法正确的是()