The question is, which number does not have a radical sign after you simplify it.
So... the square root of 1 is 1, so sqrt(1) is rational.
The square root of 2 cannot be simplified further, because 2 is not a perfect square. sqrt(2) is not rational.
sqrt(65) = sqrt(5*13). This still has a radical sign and we cannot simplify it further, so this isn't rational.
sqrt(196) = sqrt(4*49) = sqrt(2^2*7^2)=14
sqrt(196) is rational, because we get a whole number without a radical.^1
sqrt(225) = sqrt(25*9)=sqrt(5^2*3^2)=15
sqrt(225) is rational, because we get a whole number without a radical.
So, the rational radicals are: sqrt(1), sqrt(196) and sqrt(225).
Footnote 1: Not all rational numbers have to be whole ones. For example, 0.bar(11) is rational, because it can simplify into a fraction. All rational numbers are by definition, a number that can simplify into a fraction. So, whole numbers are rational, but not all rational numbers are whole.