35. He must be from Africa, __________ can be seen from his skin.

选择b是没错，不过解释错误了。

as确实可以引导方式状语，比如I did the work as my father taught me.
但是，这里是定语从句，只不过先行词不是一个名词或者代词，而是真个句子
在非限制性定语从句中，which和as可以引导定语从句修饰整个句子，注意that，where,when,why等都不行。

举个列子，They did rather badly in the maths exam,which was not what I had expected.
这前面整个“They did rather badly in the maths exam”
是我所没意料到的
还有更简单的例子，也就是as we all know结构
As we all know, china is a developping country.
这里we all know 的内容就是“china is a developping country”这整一句话。

补充一下，as引导方式状语时，从句式完整的句子，而引导定语从句时，则从句缺少成分，比如As we all know，缺少的就是know 的宾语，而宾语其实就是主句“china is a developping country”

正确答案应该是as
He must be from Africa, as can be seen from his skin.
自己读一下，和理解意思~

B as
as引导的从句通常可以省略主语。
表示方式。
Who不可以引导方式状语从句。