Which statement is true about 513? a. it is a prime number. b. it is a composite number. c. it is a whole number that is neither prime nor composite. d. it is not a whole number.

A isn't true because 513 is at least divisible by 3, so it's not a prime number.
C isn't true because all whole numbers are either prime or composite. 
D isn't true because it is neither a imaginary number, fraction, decimal, or unreal number, so therefore it must be a whole number.
B is true, because it is able to be divided by numbers other than one and itself.