Which Statement Best Describes What Happens When There Is a Change

Which statement best describes what happens when there is a change in quantity demanded?  

A)  A change in quantity demanded is shown by a shift in a given demand curve. 
B)  The demand curve shifts whenever the quantity demanded of a substitute good changes. 
C)  A change in the price of a good, other things constant, will lead to a change in quantity demanded. 
D)  The lower the price of a product, other things constant, the lower the quantity demanded.