PREP 61

原题如下：
Researchers in Germany have unearthed 400,000-year-old wooden spears from what it appears was an ancient lakeshore hunting ground as stunning evidence of human ancestors who systematically hunted big game much earlier than believed.

A. it appears was an ancient lakeshore hunting ground as stunning evidence of human ancestors who

B. it appears had been an ancient lakeshore hunting ground and stunning evidence that human ancestors

C. appears was an ancient lakeshore hunting ground and is stunning evidence that human ancestors

D. appears to be an ancient lakeshore hunting ground, stunning evidence that human ancestors (D)

E. appears that it is an ancient lakeshore hunting ground, stunning evidence of human ancestors who

此题答案是D

但我的疑问是，是否可以把“what it appears was an ancient lakeshore hunting ground ...”为一个含有主语从句的复合句。这个复合句作为介词FROM的宾语？从语法上有问题吗？