Which of the Following Is an Explanation for Price Stickiness

Multiple Choice

Which of the following is an explanation for price stickiness?
I. There are adjustment costs associated with changing prices such as the cost of printing new price lists.
II. Worker unions may forbid firms from raising prices for fear that workers may be laid off if demand for output falls.
III. Firms may have explicit long-term contracts to sell their products to other firms at specified prices.

A) I only
B) I and II only
C) I and III only
D) I, II, and III