For the linear demand curves, price elasticity of demand falls as you move downward along the demand curve. Non-linear demand curves mostly have a different price elasticity along
the entire curve since the slope changes as you move along the demand curve. On the other hand, the linear demand curves have a constant slope.As you move down a linear demand curve, the slope which is equal to the ratio of the absolute change in price to that in quantity, remains constant. Answer is A.