1. What is your name?

(Is 'what' a subject or a subjective complement?)

The subject complement is "what."

Please note that I imagine that 90% of Americans don't know this. And it really doesn't make any difference. <g>

it is a subject complement

To determine whether "what" in the sentence is a subject or a subjective complement, we need to look at the sentence structure and the role that "what" plays.

In the sentence "What is your name?", "what" is functioning as the subject of the sentence. It is the word that is performing the action or being described in the sentence. The verb "is" connects the subject "what" to the subjective complement, which is "your name."

We can confirm this by rearranging the sentence to its basic structure: "Your name is what." Here, "your name" becomes the subject, and "what" functions as the subjective complement, describing or renaming the subject.

So in this sentence, "what" is the subject, not the subjective complement.