What can be inferred from the professor?
A    He is sure that students have the knowledge about the basics about free market already.
B    He is not sure how to explain the difficult concept of the market clearing price.
C    He assumes  that students can get confused between  the concept of equilibrium and  that of the
market clearing price.
D    He thinks that the term “market clearing price” is a bit hard to understand for students.
(D)