Each of the following linear equations defines y as a function of x for all integers x from 1 to 100. for which of the following equations is the standard deviation of the y-values corresponding to all the x-values the greatest?

(a) y = x/3
(b) y = x/2 + 40
(c) y = x
(d) y = 2x + 50
(e) y = 3x - 20