请教GWD 2道语法题，太难了，谢谢指教！

路人乙

gwd第一套的第三题，完全看不懂 ，请高人不吝指教！！
万分感谢！！
3.For protection from the summer sun, the Mojave lived in open-sided, flat-topped dwellings known as shades, each a roof of poles（极点，杆子） 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
Answer: A
另外，gwd第一套的第16题，D 和E选项该如何区分，是一种什么样子的语法结构？
16.While digging in the Egyptian desert, huge fossil bones have been found by paleontologists（古生物学着）, which appears to have been the second most massive(巨大的)dinosaur(恐龙)that ever lived.
A.    huge fossil bones have been found by paleontologists, which appears to have been
B.    huge fossil bones have been found by paleontologists, which appear to be from
C.    it appears that paleontologists have found huge fossil bones that are from
D.    paleontologists have found huge fossil bones from what appears to be
E.    paleontologists have found huge fossil bones, which are from what appear to be
 
Answer:  D

sayysong

LZM语录，在GMAT中，非限制性定语从句指代物用that引导；which用于引导介宾指物。
原话赶明儿我翻翻书再抄上来。

cx_ding

我怎么感觉还是E对呢？
E which指代fossil bones，骨头来自于曾经第二大的恐龙。
D 里面的what怎么解释，请牛牛赐教。

路人乙

谢谢sayysong的解释，茅塞顿开。。。。

还有一点疑问，#16，如果没有d选项，E是不是就是正确的？

另外"E的which从句显然应该修饰fossil bones却使用了非限制性定语的形式。"非限定性定语从句为什么不对阿？

sayysong

#3
为了遮蔽夏日阳光，Mojave住在一种被称为shades的四面敞开的平顶屋子里，(这种房子)顶上是由杆子和arrowweed（？）撑起的一个长方形(结构)。
D和E中的roofs复数与后文的a rectangle不一致，可以排除。
C中with ... being ... 冗余
B中的that are being也冗余

#16
while digging ... 只能由人来担任主语，排除A，B
C中的 it appears that 一般用于描述一个客观现象，与此处的发掘化石事件语境不符，排除。
E的which从句显然应该修饰fossil bones却使用了非限制性定语的形式。