#### Answer

C does not equal to 25n

#### Work Step by Step

We can find the answer through process of elimination
A= $(5n^{\frac{1}{2}})^{2}$
=$(5)^{2}(n^{\frac{1}{2}})^2$
=25n ; it equals 25n to it is not the correct answer
B= $(5n^{\frac{1}{2}})(5n^{\frac{1}{2}})$
=25n ; it equals 25n to it is not the correct answer
D=$5^{2}(n^{\frac{2}{3}})^{\frac{3}{2}}$
=25n ; it equals 25n to it is not the correct answer
Therefore, we must conclude that C is the correct answer