Choose the true biconditional statement that can be formed from the conditional statement "if a natural number n is odd, then n2 is odd" and its converse.

a. n2 is not odd if and only if a natural number n is not odd.
b. a natural number n is odd if and only if n2 is odd.
c. a valid biconditional cannot be formed because the statement and its converse are not logically equivalent.
d. a natural number n is not odd if and only if n2 is not odd.

The answer 
mathematics rules tell that 
if A and B are two statements that are equivalents, that is also called biconditional statement, or " if and only if " statement

the general signification of biconditional statement and its converse is:
if A, then B and if B then A (the converse), A and B are equivalent statements
["If a natural number n is odd, then n2 is odd" and its converse ] does mean
A natural number n is odd if and only if n2 is odd.
the answer is B