"If and only if" sounds strange to me too. Like asking if he's a knight when Pluto is a dwarf planet. And on second reading it looks like an awkward way to say

"If and only if" sounds strange to me too. Like asking if he's a knight when Pluto is a dwarf planet. And on second reading it looks like an awkward way to say And... I think "Is one and only one of [A, B] true?" would be better. Or, (A ^ B).