​The Main Reason(s)firms in a Competitive Market Cannot Earn Positive

Multiple Choice

​The main reason(s) firms in a competitive market cannot earn positive profits in the long run is(are)

A) ​assets can quickly move in and out of the industry when demand fluctuates
B) an increase in demand leads to entry of firms which absorb the extra demand
C) a decrease in demand leads to exit of firms from the market such that there is no surplus
D) ​all of the above