we know that
Rational Number is a number that can be made by dividing two integers, and an Irrational Number is a real number that cannot be written as a simple fraction
so
case a)

------> is an irrational number
case b)

------> is an irrational number
case c)


we know that
All whole numbers are rational numbers.
therefore
the case c) is a rational number
case d)

------> is an irrational number
therefore
the answer is
is a rational number