To answer this question, we need to define what a rational and irrational number means
A rational number is a number that can be expressed as a ratio of two integers where both the numerator and the denominator in the fraction are integers.
To check if the options are rational or irrational numbers
Step 1: Find the square root of the numbers
since 2√3 cannot be expressed as a ratio of two integers, then It is not a rational number
since -9 can be expressed as a fraction:
It is a rational number