Which of the following is NOT a supported parameter type in Apex REST classes?

In Apex REST classes, parameters can be defined in various forms to handle incoming requests effectively. Blob, while a fundamental type in Apex, cannot be used directly as a parameter type for Apex REST methods. This is primarily because Apex REST processes data in a way that is compatible with HTTP, where blobs do not have a direct representation in standard HTTP requests or responses.

On the other hand, sObjects, Lists of Apex primitives, and Maps with String keys are all supported parameter types in Apex REST. sObjects allow you to represent Salesforce records, which can be passed directly in body requests. Lists enable sending collections of data, and Maps provide a flexible way to handle key-value pairs, easily mapped from JSON structures. Therefore, the correct choice highlights the limitation of using Blob within the context of Apex REST parameter types.