Which of the following lists of data has the smallest standard deviation? Select the correct answer below: A. 11, 17, 9, 4, 4, 6, 6, 9, 8, 18
B. 29, 21, 21, 28, 28, 26, 24, 24, 17, 23
C. 6, 8, 10, 6, 8, 8, 10, 7, 10, 10
D. 23, 19, 12, 19, 17, 18, 16, 10, 12, 21
E. 17, 12, 6, 6, 15, 16, 20, 20, 5, 17

Let x be the number of tree planted. With this representation, the number of bushes planted is 3x. The equation that would best represent the situation above is,
                                        (x)(75) + (3x)(20) = 810
The value of x is 6. The number of bushes planted is 18. Thus, the answer is letter C.18.