[問題]GWD13-29(10-3) 請問句意

[emilychen]

Q29(10-3亦同)
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 arrow weed
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

雖然討論區已有人在修辭上進行解答，但是這句的句意還是有點翻不出來到底是什麼意思，是否有人可以幫我解答一下，感謝呦~~
我的翻譯：
為了避免夏日陽光的照射，Mojave住在一種有開一邊、頂部為平的住所，一般知道叫shades，這種住所每一個支撐的屋頂和???是以一套三角型的柱子支撐著???。

[eggcake520]

arrowweed好像是一種箭草...
post:a strong upright piece of wood, metal etc that is fixed into the ground, especially to support something.(from Longman)

所以翻譯:
為了避免夏日陽光的照射，Mojave住在一種有開一邊、頂部為平的住所叫做shades，這每一個柱子與箭草的屋頂是以一組長方型的柱子支撐著。