Question

If something has no relevance to the topic under discussion, it is ________. extraneous

Answer 1

Extraneous means "irrelevant or unrelated to the subject being dealt with."
Hybrid means "a thing made by combining different elements."
Concomitant means "naturally accompanying or associated with."

Extraneous is the word that fits. Concomitant is actually the opposite of this.

Answer 2

I think the answer is Extraneous.