Rewrite each equation in slope-intercept form, if necessary. Then determine whether the lines are parallel. Explain,

y=-X+7

x+y =21

Are the lines parallel?

A. No, the lines do not have the same slope so they are not parallel.
B. No, since the product of the slopes of the lines is - 1, the lines are perpendicular.
C. Yes, since the product of the slopes of the lines is - 1, the lines are parallel.
D. Yes, since both lines have a slope of - 1, the lines are parallel.