How to avoid a bloodbath when the boy meets Grandma?

I’m just starting to date someone, and before too long the guy will be meeting my grandma.

They’ll get along great, BUT there is one specific topic on which they passionately disagree. Both are unswayed from their positions. It would be best for everyone if this topic didn’t come up. I’m trying to decide if:

A. I should straight-out tell Grandma to avoid that topic, although she just might bring it up anyway to try to convince the boy he’s wrong;

B. Tell the boy to lie about his college major, because if she asks and he answers truthfully, it will definitely come up;

C. Just hope it doesn’t come up and prepare something to radically change the subject if it does (like faint)

What would you do? What distracts grandmas?