OG-49 非常奇怪

ets对49中A的批驳理由是：the pronoun "which" should be used to refer to a previously mentioned noun, not to the idea expressed in an entire clause

可是许多语法书上明确写了：非限制性定语从句中，关系代词可以修饰前面整个主句，如;

Bamboo is hollow, which makes it very light.

They did rather badly in the maths exam, which was not what I had expected

以上句子在平时也不是鲜见的

再者，OG正确答案B就对了吗？这里"doubling....."分词作状语唯一的解释就是作伴随状态，其作用相当于and连接的并列句, 那么and的主语是什么？既然which找不到先行主语，那么这个分词状语又在哪里，既不是camera也不是前面的句子

晕了，请教高手

This is one of ETS' rules.