A nonprofit wants all donations related to a new direct mail appeal to be assigned...

In NPSP, the tracking of restricted funds is managed through the General Accounting Unit (GAU) and GAU Allocations. When a nonprofit launches a specific appeal (like a direct mail campaign) for a restricted fund, the system can automate the allocation of every gift received through that appeal.

Step-by-Step Implementation:

The GAU: Ensure the restricted fund is created as a General Accounting Unit record.

The Campaign: Create a Campaign record representing the "Direct Mail Appeal."

Manage Allocations: On the Campaign record, a consultant uses the Manage Allocations button (a specialized NPSP interface).

The Link: In this interface, the consultant selects the designated GAU and assigns it to the Campaign (usually at 100%).

Automation: Because of NPSP's built-in logic, any time a donation is created and linked to this Campaign (as the Primary Campaign Source), the system will automatically create a GAU Allocation record for that donation, linking it to the restricted fund.

Why other options are incorrect:

Option D: Setting a "Default GAU" is an org-wide setting. If you set the restricted fund as the default, then every gift in the system (even unrestricted ones) would go to that fund.

Option C: Simply adding a custom lookup field to the Campaign does not trigger the complex NPSP automation needed to create the Allocation records on the Opportunity. You must use the "Manage Allocations" feature to "connect" the campaign to the GAU logic.