Mono means 1 Oli mean some. Olipoly means some seller. Monopoly means one seller. Monopsony means only one buyer. Oligopsony means some (but not a lot). The idea is the the choice of some hhave impacts on the others. With only a few seller, (Oligolpies) can have long run economic profit. C is the only right answe. Please don't hesoitate to reach out for help.