Why is the elasticity of demand not equal to the slope of the demand curve?A. Because elasticity is a ratio of two changes and slope is a ratio of two changes.B. Because elasticity is a ratio of two changes and slope is a ratio of two percent changes.C. Because elasticity is a ratio of two percent changes and slope is a ratio of two changes. D. Because elasticity is a ratio of two percent changes and slope is a ratio of two percent changes.