The correct answer is B. Using signed URLs for Cloud Storage allows clients to upload images directly to Cloud Storage without proxying through the application server. This minimizes infrastructure operations overhead by leveraging Google Cloud Storage's managed service, which handles scalability, durability, and availability. Option A is incorrect because storing large files in a database is inefficient and increases database load. Option C introduces operational overhead with a web server and file store management. Option D is not scalable (creating a bucket per user is impractical) and poses security risks by transferring service account credentials.