再问大全498，是同位结构还是独立主格？

498.   Many of them chiseled from solid rock centuries ago, the mountainous regions of northern Ethiopia are dotted with hundreds of monasteries.

(A) Many of them chiseled from solid rock centuries ago, the mountainous regions of northern Ethiopia are dotted with hundreds of monasteries.

(B) Chiseled from solid rock centuries ago, the mountainous regions of northern Ethiopia are dotted with many hundreds of monasteries.

(C) Hundreds of monasteries, many of them chiseled from solid rock centuries ago, are dotting the mountainous regions of northern Ethiopia.

(D) The mountainous regions of northern Ethiopia are dotted with hundreds of monasteries, many of which are chiseled from solid rock centuries ago.（E）

(E) The mountainous regions of northern Ethiopia are dotted with hundreds of monasteries, many of them chiseled from solid rock centuries ago.

通过看以前的讨论我明白了为什么选E，但我个人认为many of them...可能是一个独立主格。以前很多人认为是个同位语，如果是个同位语为什么把be动词省略了呢（many of them are chiseled from solid rock chenturies ago），而这种省略正好是独立主格的结构。

不知我的理解对不对，请NN们指正。