Answer: B
For example, x to the power of 1/2 can be rewritten as the square root of x. Any number to the power of a fraction that has a numerator of one can just be rewritten with a radical, with the number underneath and the denominator of the fraction outside the radical. For the above problem, the 5 (numerator of fraction) can just be written as x to the power of 5, such as inside the radical in choice B. But the 7 must be outside, since x to the power of 1/7 is just X to the root of 7.