Which solution meets these requirements MOST cost-effectively?

Explanations:

Replicating the S3 bucket to all AWS Regions would significantly increase costs and complexity for maintaining multiple copies of the website. Additionally, while Route 53 geolocation routing can help route users to the nearest region, it does not provide a caching layer or reduce latency effectively compared to other options.

AWS Global Accelerator provides static IP addresses to improve availability and performance, but it is not specifically designed for serving static content like websites hosted on S3. Moreover, associating these IP addresses directly with an S3 bucket is not possible since S3 does not support direct IP addressing, which makes this option impractical.

Adding an Amazon CloudFront distribution in front of the S3 bucket allows for content caching at edge locations around the world, significantly reducing latency for users accessing the website. This solution is cost-effective as CloudFront charges are based on usage and can reduce data transfer costs compared to direct access to S3. Additionally, it improves performance by delivering content closer to users.

S3 Transfer Acceleration speeds up the transfer of files to and from the S3 bucket but does not improve the latency for end users accessing the website. It is primarily beneficial for uploads and downloads rather than serving static web content, making it less suitable for decreasing latency for website visitors compared to CloudFront.