Which of the Following Would Tend to INCREASE the Elasticity

Multiple Choice

Which of the following would tend to INCREASE the elasticity of demand for good X?

A) a new discovery allows firms to produce X at a much lower cost.
B) the percent of a consumer's income spent on good X declines.
C) a new product,Y,which can be used in place of X,is introduced.
D) both b and c
E) all of the above