According to the Microsoft Azure AI Fundamentals (AI-900) official study guide and the Microsoft Learn module “Identify features of computer vision workloads”, Optical Character Recognition (OCR) is a core capability within the computer vision domain that enables systems to detect and extract text from images or documents. OCR technology can identify printed or handwritten characters in photographs, scanned documents, or camera feeds, and convert them into machine-readable text.

In this scenario, the task is to read the numbers on runners’ shirts in race photos. These numbers are textual or numeric characters embedded within images. OCR is specifically designed for this purpose — to locate and recognize characters within visual data and convert them into usable text. Once extracted, those numbers can be cross-referenced with a database to identify each runner.

Let’s analyze why the other options are incorrect:

A. Facial recognition focuses on identifying individuals based on unique facial features, not reading text or numbers.

C. Semantic segmentation classifies each pixel of an image into categories (for example, separating road, sky, and people), but it doesn’t read text.

D. Object detection identifies and locates objects within an image (such as detecting people or vehicles) but does not extract readable text or numbers.

Therefore, since the task involves reading textual or numeric content from an image, the appropriate type of computer vision to use is Optical Character Recognition (OCR).