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 | 
