A linear equation is modified so that the rate of change is tripled, but the y-intercept remains the same. Which pair of equations could represent the original equation and the modified equation?
A. y=x+3 and 3y=3x+9
B. y=9x−2 and y=12x−2
C. y=−2x−3 and y=−2x−9
D. y=−5x+6 and y=−15x+6