Hello there! Your answer is B.
A rational number is just a number that can be expressed as a fraction.
Let's start by simplifying each number:
A.
= -4 or -4/1
B.
= 0.63245553203...
C.
= 2 or 2/1
D.
= 4 or 4/1
Out of the options given, all of them can be simplified into a fraction, except for the second one, so that means that the second one is our irrational number.