Ofall the changes that have taken place in English-language newspapers during the pastquarter-century, perhaps the most far-reaching has been the inexorable declinein the scope and seriousness of their arts coverage.
请教各位老师，在这个句子中，句首的“Of all the changes”应该理解为什么种句子成分呢？又是是一种什么语法现象呢？
Of all the changes that have taken place in English-language newspapers during the past quarter-century, perhaps the most far-reaching has been the inexorable decline in the scope and seriousness of their arts coverage.
1. of all....介词短语常用来表示 “最高级的范围”。有时为了强调或照顾句子匀称，可以置于句首。还可以用 among all ...。
2. 本句主干：Of all the changes, the most far-reaching has been... 在所有些变化中，影响最深远的是......。其中，that havetaken place in English-language newspapers during the past quarter-century，为 all the changes 的定语从句。本句放在句首是什么原因后面接了一个定语从句，主要为了句子匀称。
3. 类似例句：
The one with applejam is the best of all thedelicious cakes. =
Of all the delicious cakes, the one with apple jam is the best.
在所有美味的蛋糕中，有苹果酱的这种蛋糕是最好的。
4. 我把上句变成跟网友的句子完全一样的结构：
Of all thedelicious cakes that I have made, the best has been the one with apple jam.
