GraphQL's ability to handle hierarchical queries efficiently is a key factor in its popularity for modern web applications. It allows clients to request only the data they need, minimizing over-fetching and under-fetching of data.

To maintain data consistency in microservices, Saga strategies are often employed. The Saga pattern helps manage distributed transactions by breaking them into a series of smaller, independent steps or compensating transactions. It ensures that the system remains consistent even when multiple microservices are involved in a transaction, and failures occur.

Authorization testing is crucial in GraphQL to ensure proper access control to data and operations. This involves checking if only authorized users can perform specific actions, helping to secure the API against unauthorized access.

For handling sensitive data, the Authorization Code Flow with PKCE is recommended as it ensures secure exchange of authorization codes, reducing the risk of exposing sensitive information.

Analyzing API logs helps identify potential bottlenecks and performance issues. Increasing server resources, optimizing network bandwidth, and implementing CDNs are valid strategies but may not be the first step in troubleshooting. Understanding the specific issues from logs is crucial before taking corrective actions.

Integrating API test automation into a continuous integration pipeline can be challenging due to the lack of proper API documentation. Without clear documentation, understanding and writing test cases become difficult.

The correct option is "c) Deprecation Warning." Deprecation warnings serve as a crucial tool for notifying users about upcoming changes in APIs, allowing them to adapt and make necessary adjustments to their code. These warnings help in smooth transitions and reduce unexpected disruptions.

Load testing is essential for evaluating the performance of an API under various levels of load. It helps identify bottlenecks and weaknesses in the system when subjected to sustained use and heavy loads.

In a CI/CD pipeline, API tests are typically executed after the Deployment stage. This is because, during the Deployment stage, the application is deployed to a testing environment, allowing for comprehensive API testing to ensure the proper integration of components. API tests at this stage help catch integration issues before they progress further in the pipeline.

RESTful APIs commonly use JSON for data exchange, providing a lightweight and easy-to-read format. SOAP APIs, on the other hand, typically use XML for data exchange, which is more rigid and structured.