The correct method to make a Cloud Storage bucket public is by granting the Storage Object Viewer role to allUsers. This approach ensures that anyone on the internet can access the files without authentication. The GCP documentation recommends this method for sharing files publicly. Options A, B, and D are incorrect because: there is no make-public command in gsutil, the GCP Console does not have a 'make public' checkbox, and allAuthenticatedUsers does not provide public access as it requires authentication.