5. For protection from the summer sun, the Mojave lived in open-sided, flat-topped dwellings known as shades, each a roof of poles and arrowweed supported by posts set in a rectangle.
(A) each a roof of poles and arrowweed
(B) each a roof of poles and arrowweed that are being
(C) with each being a roof of poles and arrowweed
(D) with roofs of poles and arrowweed to be
(E) with roofs of poles and arrowweed that are
答案：A
有版主说:1.with不行，表示伴随，改变意思了。
each，强调型独立主格结构，解释说明
独立主格结构：
名+名
名+分词
名+介
名+形容词

请问独立主格与伴随有什么分别，是不是独立主格加上WITH 后及分词就可以表伴随？

多谢！请赐教！