A triangular park is enclosed on two sides by a fence and on the third side by a straight river bank. The two sides having fence are of same length $x$. The maximum area enclosed by the park is:

1. A
   $\frac{\sqrt{3}}{2}{x}^2$
2. B
   $\frac{x^3}{8}$
3. C
   $\frac{1}{2}{x}^2$
4. D
   $\pi x^2$