Which of the following libraries is NOT commonly used in AI development?

React is primarily a JavaScript library used for building user interfaces, especially for web applications. It focuses on the front-end development aspect, enabling developers to create dynamic and interactive user experiences. While React can certainly be part of an AI project, especially in developing applications that utilize AI models, it does not serve the core analytical or computational purposes typically associated with AI development libraries.

In contrast, TensorFlow, Scikit-learn, and PyTorch are all specifically designed for artificial intelligence and machine learning tasks. TensorFlow and PyTorch are deep learning frameworks, supporting a wide range of neural network architectures and operations. Scikit-learn is widely used for traditional machine learning algorithms and data preprocessing tasks. These libraries provide extensive functionalities for building, training, and deploying AI models, making them integral to the development process in this field. Therefore, React stands apart from these options as it does not fulfill a primary role in AI development.