Which of the following is an example of a pre-built function in Azure Cognitive Services?

The correct answer is image recognition because it represents a specific capability offered by Azure Cognitive Services that is readily available for use without the need for extensive customization or additional development. Azure Cognitive Services includes various APIs and tools that allow developers to integrate intelligent features into applications effortlessly. Image recognition leverages machine learning and artificial intelligence to analyze and identify objects, people, and scenes within images.

On the other hand, options like data cleaning, model training, and feature selection are more fundamental processes that typically require a significant amount of custom development and data preparation. These activities are often part of the data science workflow where data scientists build and refine machine learning models. They are not pre-built functions available out of the box in Azure Cognitive Services, but rather steps that practitioners undertake to prepare their data and models before potentially utilizing services like image recognition.