What is an effective method to mitigate this?

You run an ad-supported photo sharing website using S3 to serve photos to visitors of your
site. At some point you find out that other sites have been linking to the photos on your site,

causing loss to your business. What is an effective method to mitigate this?

A.
Store photos on an EBS volume of the web server

B.
Remove public read access and use signed URLs with expiry dates.

C.
Use CloudFront distributions for static content.

D.
Block the IPs of the offending websites in Security Groups.