Answer:
B. will increase
Step-by-step explanation:
Assuming that 50 firms in a monopolistically competitive industry in country A and 50 firms in the same monopolistically competitive industry in country B. If country A and country B engage in international trade, we expect that the total number of firms in this industry will increase .Because after trade, assuming firms in both countries make economic (excess) profits, this will attract entry of other firms into the industry in both markets. So, number of firms will increase. The correct answer is Option (B).