Question

Which biconditional statement is true?

A. A number is divisible by 9 if and only if it ends in 3.
B. A quadrilateral is a square if and only if it has four right angles.
C. The sum of two integers is positive if and only if the two integers are positive.
D. A number is an even number if and only if it is divisible by 2

Answer 1

Let us evaluate the given statements.
A, A number is divisible by 9 if and only is it ends in 3.
23/9 is not divisible.
FALSE

B. A quadrilateral is a square if and only if it has four right angles.
A rectangle is a quadrilateral with four right angles, but it is not a square.
FALSE

C. The sum of two integers is positive if and only if the two integers are
positive.
12 + (-10) = 2 (positive).
FALSE

D. A number is an even number if and only if it is divisible by 2.
Thi is true by definition.
TRUE

Answer: D