The numerator of the exponential is kept where it is whereas when converting an exponential into a radical, the denominator becomes the root of the variable.
(x ^ (3/4)) will be equal to the root of the value x ^ 3 i.e. .
(y ^ (1/4)) will also be equal to the root of y's value i.e. .
Out of the given options, options 1, 3 and 4 have cube roots so they cannot be the answers. Option 2 has the value of x correct but the value of y will equal y ^ (1/2) so it is also incorrect.