the dogs greedily devoured what was left of the cake.这句话中的wh

the dogs greedily devoured what was left of the cake.这句话中的what was left of the cake是被动语态吗? 而且这里的of the cake这用法我不是很明白,求解释这句子可以改成这样吗?the dogs greedily devoured the left cake 动词加ed可以作形容词用,但是leave不能加ed,所以我用过去分词的形式,请问动词加ed的形式是所有动词都能用还是只是部分动词而已the dogs greedily devoured the cake which was left by people 这句这样写有问题吗?还有一个问题,greedily devour 这副词 “贪婪地” 来修“饰狼吞虎咽地吃” 总感觉有点奇怪,请问他这样些是课文的需要还是外国人本身就这样写 用一个夸张的副词来修饰一个夸张的动词, 直接写成greedily eat不好吗 求解释 感谢回答!