The correct answer is B because project-wide SSH keys allow users to access all instances within a project that permit such keys. This method is efficient as it applies the keys across the entire project with a single command. The command gcloud compute project-info add-metadata --metadata-from-file ssh-keys=[LIST_PATH] is used for this purpose.

• Option A is incorrect because gcloud compute ssh is designed for connecting to instances, not for uploading SSH keys.
• Option C is incorrect because while it does upload keys, it does so on an instance-by-instance basis, which is less efficient than a project-wide approach.
• Option D is incorrect because there is no user interface option for uploading SSH keys in bulk, making this method impractical for large teams or projects.