AWS Lambda automatically sends function execution logs to Amazon CloudWatch Logs when logging is enabled in the function code. However, this logging capability depends on the Lambda execution role having the appropriate permissions. According to the AWS Certified Security -- Specialty Study Guide, the execution role must include permissions such as logs:CreateLogGroup, logs:CreateLogStream, and logs:PutLogEvents.

If these permissions are missing, Lambda cannot create log groups or streams, and no execution logs will appear in CloudWatch Logs---even though the function was successfully invoked. This is the most common reason Lambda logs are unavailable during forensic investigations.

Option B is incorrect because Lambda logs are stored in CloudWatch Logs regardless of whether the invocation source is API Gateway, EventBridge, or another AWS service. Option C is incorrect because CloudWatch Logs does not require direct S3 permissions from the Lambda execution role. Option D is irrelevant because Lambda versions do not affect logging behavior.

AWS documentation emphasizes verifying execution role permissions as a first step when Lambda logs are missing.

Referenced AWS Specialty Documents:

AWS Certified Security -- Specialty Official Study Guide

AWS Lambda Execution Roles

Amazon CloudWatch Logs Integration with Lambda