What Assumption(s) Is (Are) Necessary to Generate a Kinked Demand

Multiple Choice

What assumption(s) is (are) necessary to generate a kinked demand curve?

A) all firms in the industry ignore the price changes made by any one firm
B) any price decrease will be ignored but price increases will be followed
C) all firms will follow a price decrease but will ignore any price increase
D) all price changes made by any firm will be followed by all of the other firms
E) price can increase, but not decrease