The solution to 5 × 1 will be what kind of number?
B. Perfect square
D. A multiple of 2
5×1 = 5 .. which is PRIME (because you can only divide it by 5 or 1).
Looking at the other options :
It’s odd and not even .. so it’s not a multiple of 2 either (only even numbers are)
and because it’s prime it isn’t the square of anything either.