题目选项分析

Some airlines allegedly reduce fares on certain routes to a level at which they lose money, in order to drive competitors off those routes. However, this method of eliminating competition cannot be profitable in the long run. Once an airline successfully implements this method, any attempt to recoup the earlier losses by charging high fares on that route for an extended period would only provide competitors with a better opportunity to undercut the airline's fares.

Which of the following, if true, most seriously weakens the argument?

【选项】In some countries it is not illegal for a company to drive away competitors by selling a product below cost.