In the third month of a study, a sugar maple tree is 86 inches tall. In the seventh month, the tree is 92 inches tall. Assuming the tree grows at a constant rate every month, what is the rule for the height of the tree during the nth month?
A. an = 83 + 1.5(n – 1)
B. an = 83 + 1.5(n + 1)
C. an = 86 + 2(n – 1)
D. an = 86 + 2(n + 1)
