A nonprofit wants to record the most recent Opportunity close date on Contact records.

In NPSP, aggregating data from child Opportunity records to the parent Contact or Account record is handled by the Rollup engine. While there are several ways to do this in Salesforce, Customizable Rollups are the standard NPSP tool for this requirement.

Why Customizable Rollups (C) are the best fit:

Cross-Object Support: Standard Roll-up Summary fields (Option B) only work if there is a Master-Detail relationship. Because the relationship between Opportunities and Contacts in NPSP is technically a Lookup relationship (managed through Opportunity Contact Roles), standard roll-ups cannot be used.

Logic and Filtering: Customizable Rollups allow the consultant to define specific "Filter Groups." For example, you can set the rollup to only look at "Closed/Won" donations and ignore "In-Kind" gifts.

Operation Types: To get the "most recent" date, the consultant sets the rollup operation to MAX. The system will look at all qualifying Opportunities, find the one with the latest (highest) date, and write that date to the target field on the Contact.

Automation: Every time a new Opportunity is added or updated, NPSP's nightly batch (or real-time triggers) will re-calculate the value. If a new gift arrives with a more recent date, the old value on the Contact will be overwritten automatically.

Formula fields (Option A) cannot be used because they can only pull data up from a parent to a child, not aggregate multiple child records into a single parent field.