If two lines are perpendicular, which statement must be true? a) the product of their slopes is 1. b) their slopes are opposites. c) their slopes are equal. d) the product of their slopes is -1.

If two lines are perpendicular, the statement that must be true is : D. The product of their slopes is -1

Lets say that a line has a slope of 2, the line which perpendicular to that line would have a slope of -1/2

Which means, the product would be 2(-1/2) = -1

hope this helps