Use the formula (n - 2) * 180 to find the sum of the measures of the interior angles of a polygon, where n is the number of sides.
An octagon has 8 sides, so plug in 8 for n.
(8 - 2) * 180 = 1,080
Now divide this by the number of sides of an octagon, 8.
1,080/8 = 135
The measure of one interior angle of an octagon is 135 degrees.
D) 135