A wildlife biologist is interested in the relationship between the number of chirps per minute for crickets (y) and temperature. Based on the collected data, the correlation coefficient r = 0.88, r^2 = 0.77, and the least squares regression line is y = 10.53 + 3.412x, where x is the number of degrees Fahrenheit by which the temperature exceeds 50°. The percentage of variation in the values of y that can be explained by the least-squares regression is closest to:
a. 77%
b. 88%
c. 11%
d. 12%
e. 23%