GWD8-Q3

For protection from the summer sun, the Mojave lived in open-sided, flat-topped dwellings known as shades, each a roof of poles and arrow weed supported by posts set in a rectangle.

A. each a roof of poles and arrow weed

B. each a roof of poles and arrow weed that are being

C. with each being a roof of poles and arrow weed

D. with roofs of poles and arrow weed to be

E. with roofs of poles and arrow weed that are

   Answer: A

A 正确，each引导的强调型独立主格结构，强调句未的复数名词，形式为：句子+复数名词结尾，each+介词短语/形容词短语/名词短语/-ing形式/-ed形式。

B being风险结构，排除。

C being风险结构，排除。

D roofs与a rectangle不匹配

E roofs和arrowweed后面的that are从句有歧义，不明确修饰对象，且roofs与a rectangle不匹配

为什么roofs与a rectangle不匹配呢？如果D选项的to be去掉可以吗？觉得读起来很通的样子。。。。求大神解释