While digging in the Egyptian desert, huge fossil bones have been found by paleontologists, which appears to have been the second most massive dinosaur 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

没明白D的意思，D、E的意思截然不同，但E有个致命的错误，即appear应该改为appears，但是D好像缺了从句的主语啊，from what后面没有说是什么appears to be。。。，这句到底是怎么回事啊，请指教～～

这里what appears to be...应该是名词性从句吧，作用相当于名词

What 引导主语从句时在句时在从句中充当句子成分，所以what就是appears to be 的主语。