Which of the following is NOT a potential use case for using AWS Lambda?

Answer options:

A.Periodically check the log files for errors in CloudWatch or CloudTrail and send out notifications through SNS.
B.Download S3 bucket objects of size varying between 500 MB-2 GB to a Lambda Ephemeral disk or temp location, read and analyze them for keywords and add the keywords to the metadata of file object for search purposes.
C.Schedule a job and invoke a Lambda function to generate AWS resource usage reports based on certain tags.
D.A website with highly scalable backend layer that will persist data into RDS or DynamoDB.

Answer: B
Option A is a potential use case for AWS Lambda. You can use Lambda as a scheduled event and read log files from AWS CloudWatch or CloudTrail and report any errors through SNS notifications.
Option C is a potential use case.
For more information on scheduling Lambda functions, refer to documentation here. 
https://docs.aws.amazon.com/lambda/latest/dg/with-scheduled-events.html?shortFooter=true
Option D is a potential use case.
You can host the web frontend on S3 and accelerate content delivery with Cloudfront caching. The web frontend can send requests to Lambda functions via API Gateway HTTPS endpoints. Lambda can handle the application logic and persist data to a fully managed database service.
(RDS for relational, or DynamoDB for non-relational database). You can host your Lambda functions and databases within a VPC to isolate them from other networks.
Here is the documentation for building a serverless website.
https://aws.amazon.com/getting-started/projects/build-serverless-web-app-lambda-apigateway-s3-dynamodb-cognito/
Option B looks like a potential use case. But the scenario will fail due to the /tmp directory space limitation.