Positioning by product class involves which of the following examples?

Positioning by product class is a strategy where a company defines its product in relation to other product categories, highlighting how it fulfills similar needs in a different way. The example of Amtrak being positioned as an alternative to airplanes fits this definition perfectly. Amtrak emphasizes its role not merely as a train service but as a viable option for travelers who might consider flying, especially for routes where both modes of transportation are available. This positions Amtrak within the context of transportation options, allowing consumers to weigh their choices among different travel classes, such as air travel and train travel.

The other examples provided do not utilize positioning by product class. Apple targeting students emphasizes a demographic marketing approach rather than a competitive product category. Netflix providing movie subscriptions focuses on the specific service of streaming rather than comparing itself directly to a different product class, such as traditional television or cinema. McDonald's focusing on value meals centers on pricing strategy and catering to cost-conscious consumers, which also does not involve categorizing the product in relation to another product class. Therefore, Amtrak’s approach distinctly illustrates positioning by product class, making this the correct option.