Answer:
B. Firm A engaged in predatory pricing.
Explanation:
Since Firm A and B are the only two companies that sell this good
Firm A decided to price its subscriptions below average variable cost that is it lowered it's prices which made Firm B to also lower it's own, but they went bankrupt and exited the market. Firm A then raised prices by 40% and is currently earning large, positive economic profits.
Based on this, Firm A engaged in predatory pricing.
Predatory pricing is a marketing or pricing strategy that has to do with lowering the cost of goods and services for a short-term, in order to make competitors lower their price, making them to go bankrupt in the process and thereby exiting the market.