For what value(s) of k will the expression $$p + \frac{1}{9}\sqrt{p}+k^{2}$$

A

$$k = \pm \frac{1}{21}$$

B

$$k = \pm \frac{1}{18}$$

C

$$k = \pm \frac{1}{9}$$

D

$$k = \pm \frac{1}{8}$$