A scatter plot with a line of fit is given. Scatter plot with points at (1, 7), (1, 5), (2, 5), (3, 4), (3, 5), (4, 4), (5, 4), (6, 3), (6, 1), and (8, 1), with a line of best fit drawn at y=6.7−0.72x. Which of the following is the most reasonable estimate of the correlation coefficient?

a. -0.9

b. -0.7

c. -0.5

d. -1.0