He was educated at a local grammar school, _______ he went on to Cambridge.

A．from which

B．after that

C．after which

D．from this

当运动部件低速运动时，主动件匀速运动，被动件往往出现明显的速度不均匀的跳跃式运动，即时走时停或者时块时慢的现象。这种现象称为（）。