In the sentence “As it turns out, despite a promising first few months of the experiment, what Miller discovered in the end was that the very technology he’d begun to criticize actually had very little, if anything, to do with his life’s problems.” (Para.3, L1-5), “what Miller discovered in the end was that…” serves as a subject in the main sentence (充当主句的主语), therefore, “what” was used to introduce a subject sentence here （what 引导一个主语从句）.

A. 对
B. 错