题目选项分析

Hoping to attract new customers, World Air airline is planning to offer its World Flights bonus plan for customers who fly more than six flights in any year. World Flights will entitle each customer who qualifies for one free domestic, round trip flight per year. More than 25% of World Air customers will qualify for this plan. Even with these free flights, World Air expects to increase profits substantially.

Which of the following, if true, would most seriously weaken the above argument?

【选项】The World Air unions recently agreed to new contracts, featuring a 5% across the board wage increase rather than the 10% the unions had wanted.