Explanation

Amazon Rekognition is the correct answer because it is AWS's service for image and video analysis using machine learning. It can:

• Detect and recognize faces in images and videos
• Analyze video streams in real-time
• Identify people based on facial recognition
• Track individuals across multiple frames

This makes it perfect for automated video analysis to identify employees accessing offices.

Why the other options are incorrect:

• Amazon Polly: A text-to-speech service for converting text into lifelike speech
• Amazon Cognito: A user authentication and identity management service
• AWS Lambda: A serverless compute service for running code without provisioning servers

These services don't provide video analysis capabilities required for identifying people in video footage.