精通新概念英语第四朋友,请问第四册18课里的这句话为什么用过去时态?

问题描述:

精通新概念英语第四朋友,请问第四册18课里的这句话为什么用过去时态?
They are constantly after the turtles,who peacefully submit to all sorts of indignities.One young calf especially enjoyed raising a turtle to the surface with his snout and then shoving him across the tank like an aquaplane.
这句话里enjoyed 为什么用过去时态?

有多种可能,最大的可能是这头海豚已经挂了,是讲它生前的事,第二个可能是这头海豚已经老了,没法再玩这么刺激的游戏了.