How Does the Concept of Elasticity Allow Us to Improve

How does the concept of elasticity allow us to improve upon our understanding of supply and demand?

A) Elasticity allows us to analyze supply and demand with greater precision than would be the case in the absence of the elasticity concept.
B) Elasticity provides us with a better rationale for statements such as "an increase in x will lead to a decrease in y" than we would have in the absence of the elasticity concept.
C) Without elasticity, we would not be able to address the direction in which price is likely to move in response to a surplus or a shortage.
D) Without elasticity, it is very difficult to assess the degree of competition within a market.