请教曹老师:
It is almost always due to some very special circumstances that traces of land animals survive, as by falling into inaccessible caves, or into an ice crevasse, like the Siberian mammoths, when the whole animal is sometimes preserved, as in a refrigerator. This is what happened to the famous Beresovka mammoth which was found preserved and in good condition. In his mouth were the remains of fir trees - the last meal that he had before he fell into the crevasse and broke his back.
1)这个 as by falling into inaccessible caves 怎么分析理解?这是比较句吗?
2)这个when the whole animal is sometimes preserved - 其中when是什么含义和用法?
3)这个This is what happened to the famous Beresovka -This指代前句内容,what是缩合关系代词=the thing that吗?(不是疑问代词=什么?)