Find the standard deviation for the given sample data. Round your answer to one more decimal place than the original data.
$\begin{array}{lllllllll}18 & 18 & 18 & 9 & 15 & 5 & 10 & 5 & 15\end{array}$
A. 1.6
B. 5.4
c. 5.1
D. 5.8

Step 1 ：Calculate the mean (average) of the data set: \(\frac{18+18+18+9+15+5+10+5+15}{9} = 12.555555555555555\)

Step 2 ：Subtract the mean from each data point and square the result: \((18-12.555555555555555)^2, (18-12.555555555555555)^2, (18-12.555555555555555)^2, (9-12.555555555555555)^2, (15-12.555555555555555)^2, (5-12.555555555555555)^2, (10-12.555555555555555)^2, (5-12.555555555555555)^2, (15-12.555555555555555)^2\)

Step 3 ：Calculate the mean of these squared differences: \(\frac{29.641975308641978+29.641975308641978+29.641975308641978+12.641975308641975+5.975308641975309+57.08641975308642+6.530864197530863+57.08641975308642+5.975308641975309}{9} = 26.02469135802469\)

Step 4 ：Take the square root of the result: \(\sqrt{26.02469135802469} = 5.101440125888443\)

Step 5 ：Round the result to one more decimal place than the original data: \(5.101440125888443 \approx \boxed{5.1}\)