So I would guess that we all have been at the checkout with 10-20 jugs of bleach in our carts. Typically the cashier will wonder what it is all for and after a while they just have to ask. "What do you need all that bleach for?"
My favorite answer is to keep a straight face and reply, "It is the only thing I know that works well in removing blood stains off the basement floor." You should see their faces.
What is your favorite reply?