What explains the industry trend of continuous shift towards "spend-based" loyalty programs? Group of answer choices A. It is simpler to communicate and makes branding and marketing activities much more straightforward. B. It is much easier to manage spend-based programs than points-based or segment-based programs. C. It is more profitable, as airlines feel they best incentivize customers to spend a lot rather than just to travel long distances. D. It is driven by regulatory factors to avoid any potential discrimination between different customers traveling on different routes