Which of the following tasks can NOT be done using the Informatica Cloud ReST API?

The choice selected indicates that creating new users is a task that cannot be accomplished using the Informatica Cloud ReST API. This is correct because the ReST API primarily focuses on operations related to data integration tasks such as managing task flows, schedules, and connections rather than user management functionalities. User creation and management typically involve administrative interfaces or specific administrative APIs that may not be exposed through the ReST API, as these tasks often require higher security measures and different protocols.

In contrast, the other options involve operations that are well within the scope of the Informatica Cloud ReST API. For instance, updating schedules allows for dynamic management of task execution timing, starting task flows directly interacts with the data processing aspects of integration, and deleting connections pertains to managing the environment's data sources within the integration framework. All of these functions are aligned with the capabilities provided by the ReST API, making them permissible actions.