The correct answer is: A. Inter-firm rivalry.
Cartels are a form of oligopoly in which a small number of firms collude to fix prices and output. This can lead to higher prices and lower output for consumers, as well as lower profits for the firms in the cartel. However, cartels are often unstable and do not survive for long. This is because there is always a temptation for one firm to cheat on the cartel and undercut the prices of the other firms. This can lead to a price war, which can destroy the cartel.
Inter-firm rivalry is the competition between firms in the same industry. It can take many forms, such as price competition, advertising competition, and product competition. Inter-firm rivalry can be intense in oligopolistic markets, where there are a small number of firms. This is because each firm has a large share of the market, and any changes in price or output by one firm can have a significant impact on the other firms in the market.
Inter-firm rivalry can lead to a number of outcomes, including lower prices, higher quality products, and more innovation. However, it can also lead to higher costs, lower profits, and even bankruptcies.
In conclusion, cartels under oligopoly do not survive for long because of inter-firm rivalry. This is because there is always a temptation for one firm to cheat on the cartel and undercut the prices of the other firms. This can lead to a price war, which can destroy the cartel.