A rational number is a number that can be written as a fraction.
The square root of 34 is equal to ~5.83. This number cannot be written as a fraction.
Pi is not a rational number. Its digits stretch into infinity and it does not have any factors.
The square root of 64 is a rational number. The square root of 64 is 8, which can be written as a fraction, as well as being an integer.
The square root of 102 is equal to ~10.1. This is not a rational number and cannot be written as a fraction.
Therefore, the square root of 64 (Or 8) is a rational number.
Hope this helps! :)