Consider a positive integer, which of the following biconditionals is true? (Check all that apply.)
a) "n is odd if and only if n squared is odd."
b) "n is even if and only if n squared is even."
c) "n is divisible by 3 if and only if n squared is divisible by 3."
d) "n is a prime number if and only if n squared is a prime number."