Answer:
a. True
Step-by-step explanation:
A competitive market is a market in which there are many buyers and sellers. Also, sellers have similar goods and and they don't have the power to influence the market. This means that in a competitive market companies have to accept the price define by the market and if the price is less than average total cost for all possible levels of production, a firm in a competitive market will choose to exit (or not enter) the market as it doesn't have the possibility to do something to influence the price and it won't be able to make a profit. According to that, the statement is true.