Which term best describes cheap flights according to the woman?

The term that best describes cheap flights, according to the context of the question, is often understood to be 'cost-effective.' This term indicates that the flights provide good value for the amount of money spent, allowing travelers to save on expenses while still being able to travel. Cost-effectiveness in this context speaks to the economic advantages of flying at lower prices, making air travel more accessible to people.

While convenience refers to the ease of booking or the logistics of travel, it doesn't specifically address the monetary aspect that cheap flights embody. Similarly, 'harmful' typically conveys negative consequences, which does not apply to the concept of cheap flights in a general sense. 'Efficient,' on the other hand, generally relates to the effectiveness of time and resources used, which may not directly correlate with the idea of flights being cheap. In contrast, 'cost-effective' clearly captures the essence of what makes cheap flights appealing to many travelers.