Answer:
The number which is a rational number is:

Explanation:
We know that a rational number is a number than can be expressed in the form of:
p/q
where p is an integer and q is a rational number.
1)

It could be written as:

As the number inside the square root is not a whole square term hence the number is not a rational number.
4)

As done above.
The given number is not a rational number.
3)

This number could also be written as:

which could again be written in simplified form as:

As the square root term is retained in the expression.
Hence, this number is not a rational number.
2)

This number could also be written as:

As we could see that the number could be easily expressed in the form of p/q.
Hence, the number is a rational number.