grammar - Could "are he" be correct?

I was just trying to formulate a sentence in an email, and wanted to reference a third person, inquiring as to which of something that person was referring in the forwarded mail message.

Is it:

"About which things is he talking?"

or

"About which things are he talking?"

Just FYI I originally had the "about" at the end. Not grammatically correct but no one talks like that anyway.

There seem to be conflicting rules here, but I don't know which one applies. Normally, with sentences like "What is he doing?" the "is" is part of "is talking," and similarly the second person "are talking." This would indicate that the first version is correct. But you could also argue that the helper verb applies to "things", and so should be "are" because "things" is plural.

I started to think that "is he" is correct, because if you turn the sentence around to answer it, you get "He is talking about those things" and not "he are talking". But still, there are other sentences like "Which gifts is he bringing to the party?" Now that just feels wrong, saying "gifts is" like that. But is it correct?

Answer

As, he is the subject of the sentence here, you need to match the singular, so the correct construction uses is.

About which things is he talking?

Similarly, your other example also needs is for the same reason.

Which gifts is he bringing to the party?

Things and gifts are the objects of these verbs and not the subjects so don't let them fool you. Imagine replacing them with what, for example and see how it sounds.

What is he bringing to the party?

vs.

What are he bringing to the party?