What is the simplest form of expression

It should be A

First you should reduce the fraction

Subtract the exponent by its common variables;
x^8 - x^2 = x^6
y^9 - y^4 = y^5

Now your equation should be \frac{ \sqrt{6x^{6}y^{5} } }{ \sqrt{5} } 

Then you should simplify your radical,
there are 3 groups of 2 in the x variables and 2 groups of 2 in the y variables, as a result, the x and y go outside the square root, and one y variable remains in the root (as there wasn't enough y's to make another group of 2) this should be over 5