Final answer:
Registering a new server in the S1 Pool adds a new Member to the pool.
Step-by-step explanation:
To add a new Member to an S1 Pool, the correct action is D) Registering a new server in the S1 Pool. When you register a new server in the S1 Pool, it becomes a part of the pool and contributes to the pool's resources and workload distribution. This helps in improving the performance and availability of the pool.