Calculate the Standard Deviation of the Given Random Variable X $\sigma = 10.8$

Multiple Choice

Calculate the standard deviation of the given random variable X. Please round your answer to two decimal places.
Forty-five darts are thrown at a dartboard. The probability of hitting a bull's-eye is 0.4. Let X be the number of bull's-eyes hit.

A) $\sigma = 10.8$
B) $\sigma = 18$
C) $\sigma = 4.24$
D) $\sigma = 3.29$
E) $\sigma = 5.4$