Question: In the context of Generic Authentication Architecture (GAA) and Generic Bootstrapping Architecture (GBA) as per 3GPP standards, what is a REQUIRED INPUT for the `Nhss_GbaSDM_Subscribe` service operation to authorize updates for an NF consumer?
Option 1: Subscription Data
Option 2: Result Indication
Option 3: NF Type, GBA Subscriber data type(s), Key for GBA Subscriber data type(s)
Option 4: Service Operation Name
Explanation: For the `Nhss_GbaSDM_Subscribe` service operation to successfully authorize and subscribe an NF consumer for updates, it necessitates verification of the consumer's legitimacy and specificity of the requested data. Thus, providing the **NF Type** (to identify the type of network function requesting the subscription), **GBA Subscriber data type(s)** (to specify what kind of subscriber data is being requested), and the **Key for GBA Subscriber data type(s)** (for secure access to the specified data) are all crucial. These inputs collectively ensure that the Home Subscriber Server (HSS) can appropriately validate the request and manage subscriptions securely, making them required inputs for this operation.