Is ab  perpendicular to cd? explain. yes, because the slope of ab  is 5/3  and the slope of cd  is -3/5. yes, because the slope of ab  is 4/3  and the slope of cd  is -3/4. no, because the slope of ab  is 5/3  and the slope of cd  is -3/4. no, because the slope of ab  is 4/3  and the slope of cd  is -3/5.

Although we are not outrightly given with the illustration showing lines AB and CD, we may determine if they are perpendicular based on their slopes. 

For pair of perpendicular lines, the product of their slopes should be equal to -1. This means that the slopes are multiplicative inverses of each other. We then, inspect each choice.

(a) (5/3)(-3/5) = -1
(b) (4/3)(-3/4) = -1
(c) (5/3)(-3/4) = -5/4
(d) (4/3)(-3/5) = -4/5

The answer could either then be a or b.