In a “last-click” attribution model, Google Analytics will attribute all of the conversion credit to which source(s)?

In a "last-click" attribution model, all conversion credit is assigned to the final marketing activity that directly preceded the conversion. This model prioritizes the touchpoint that immediately led to the sale or goal completion. The "first marketing activity" model would give all credit to the initial interaction. "Single assisted conversion" and "all assisted conversions" refer to scenarios where other marketing activities contributed to the conversion but were not the final touchpoint; these are considered in multi-channel attribution models, not last-click.