Which of the following is NOT an example of an Irrational Number?

Question

Which of the following is NOT an example of an Irrational Number?

4.2

square root of 5

5.212573...

pi

Answer 1

4.2 definitely is not. It can be written as 42/10,
the quotient of 2 integers.
As for 5.212573..., one can't say, because
we don't know if this decimal is repeating.

Answer 2

4.2