The correct answer is Provision an Amazon Elastic File System (Amazon EFS) and mount it on each Linux-based web server for shared access. Amazon EFS is a fully managed, scalable, and NFS-compatible file system that is ideal for Linux workloads requiring shared file storage. It allows multiple EC2 instances to mount and access the same file system concurrently, which is essential when applications require shared access and cannot be modified to work with object storage or other non-standard file systems.

The option Attach a General Purpose SSD (gp3) Amazon EBS volume to all the web servers for shared file access is invalid. Amazon EBS volumes can only be attached to one EC2 instance at a time unless configured in a complex shared storage cluster, which is not straightforward and doesn't meet the application's unmodifiable constraint.

The choice Create an Amazon S3 bucket and configure the web servers to read from it directly is incorrect because S3 is object storage and requires changes to the application to interact with it using HTTP-based APIs. Since the application cannot be changed, this option is not feasible.

The response Deploy an Amazon CloudFront distribution with an S3 bucket as its origin and serve the files through CloudFront is also not viable. While CloudFront provides caching and distribution, it does not support POSIX-style shared file access required by many Linux applications and would require application changes to access files via HTTP endpoints.

This question is important because it evaluates your understanding of file storage services in AWS and how they integrate with Linux-based applications that require shared access. The key is recognizing the need for a POSIX-compliant shared file system, which rules out EBS and S3-based solutions and highlights EFS as the correct fit.

The trick to answering this question correctly is focusing on the constraint that the application cannot be modified and requires traditional shared file system access. This makes EFS the only viable and efficient solution.

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