那么难的题目为啥没人关心啊gwd-10-3

For protection from thesummer 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

答案选A，想不通，我选了E，题目意思都不太明白，请各位大侠帮忙看看