Final answer:
The correct variable type for requesting a catalog item on behalf of another user is the 'Requested For variable'. This type identifies the beneficiary of the request and differs from variables like 'Assigned To', 'Initiator', and 'Approver'.
Step-by-step explanation:
When requesting a catalog item on behalf of another user, the correct variable type to use is a. Requested For variable. This variable type is specifically designed to represent the user for whom the item is being requested. The 'Requested For' field typically appears on the form when a service request is being made on behalf of someone else and allows the requester to specify the actual beneficiary of the service or item. This is different from the 'Assigned To' variable, which is used to indicate the individual responsible for fulfilling the request, the 'Initiator' variable, which could denote the person who started the request, and the 'Approver' variable, which is used for the individual who approves the request.