Answer: Third Option is correct.
Explanation:
Since we have given that
1) 1.5- it is a rational number as it can be written in
form.
i.e.

2)
- It is a rational number as it is written in
form.
3) 2.3 - It is a rational number as it can be written in
form.
i.e.

4) pi - It is irrational number as it can't be written in
form.
Hence, Third Option is correct.