GWD TN8 SC题求问

KellyLu961031

GWD TN8 SC
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 ( that are 就够了，没必要加are being, wordy; that are 和E 一样，不优选）  
•        C. with each being a roof of poles and arrowweed  
•        D. with roofs of poles and arrowweed to be (没有将要的意思，杀，语义）
•        E. with roofs of poles and arrowweed that are (that 修饰不清楚，跳跃修饰，不优选）

求问A和C怎么解释，感觉我没太读懂这句话什么意思，就选不出来A和C.
答案是A。

Fiona09

https://gmat.la/question/GMATLA-SC-2 传送门~