A. Incorrect, because: Although an app could be built on App Engine to adjust physical inventory in real time, this is not a built-in feature of App Engine itself. It's rather a feature of the application built on top of it.
B. Correct, because: App Engine is designed to scale automatically in response to increases or decreases in traffic. This feature is particularly useful in the case of seasonal sales, where traffic can have significant spikes.
C. Incorrect, because: While it's possible to schedule maintenance tasks, it's not a key feature that helps in handling the high load during seasonal sales.
D. Incorrect, because: Recommending the right products to customers is a feature of personalized recommendation services, which would need to be built into the application. App Engine doesn't inherently provide such features.