Identify the market structures and economic concepts described in the following multiple-choice questions.

Here are the answers to the questions:

Question 12: Product differentiation is the most important feature of
B) Monopolistic competition

Question 13: Under monopoly, monopolist can determine
C) Price and output

Question 14: The production function is a technical relation between
B) Input and output

Question 15: Average revenue line is also known as
C) Demand line