Final answer:
Access Control Lists (ACLs), Bucket Policies, and Access Points can be used to grant external accounts access to an S3 bucket.
Step-by-step explanation:
The S3 feature that can be used to grant external accounts access to an S3 bucket is Access Control Lists (ACLs). ACLs allow you to specify the permissions for individual AWS accounts or for predefined groups that you create within your own account. You can use ACLs to grant permissions for read or write actions on the bucket or its objects.
Another option is to use Bucket Policies. Bucket policies let you manage permissions for an entire S3 bucket or for specific objects within the bucket. You can use bucket policies to grant access to specific IP addresses, VPCs, users, roles, or AWS accounts.
Lastly, you can also use Access Points to grant external accounts access to an S3 bucket. Access Points provide a unique DNS name that you can share with external accounts, allowing them to access specific buckets or prefixes within a bucket based on the permissions you set.