A daily budget represents the average amount an advertiser is willing to spend per day on an ad set or campaign. Meta's delivery system is designed for flexibility; it may spend up to 25% more than the set daily budget on days with high-potential opportunities and less on other days. However, the system ensures that the total spend for a calendar week (Sunday to Saturday) will not exceed the daily budget multiplied by seven, thus maintaining the specified daily average over that period.

A. This is incorrect. It describes a lifetime budget, which is set for the entire campaign duration, not a daily spend. Also, daily spend is an average, not a strict maximum.

B. This is incorrect. Ad spend is never an "exact" amount due to the dynamic nature of the ad auction. It also incorrectly refers to the campaign's duration.

C. This is the definition of a lifetime budget, which is the total amount an advertiser agrees to spend over the entire run of an ad set or campaign.

1. Meta Business Help Center, "About campaign budgets": Under the "Daily budget" section, it states, "A daily budget is the average amount you're willing to spend on an ad set or campaign each day." This directly supports the correct answer's definition.

2. Meta Business Help Center, "About our daily spending limit for daily budgets": This document clarifies the "average" concept: "To give you more flexibility to get results, we may spend up to 25% more than your daily budget on some days and less on others... For example, if your daily budget is $10 USD, we may spend up to $12.50 USD on a given day." This refutes the idea of a "maximum" or "exact" daily spend.

3. Meta Blueprint, "100-101: Meta Certified Digital Marketing Associate Study Guide": In the section "Set your campaign budget," the guide explains, "With a daily budget, you set an average amount to spend per day." This official exam preparation material confirms that the daily budget is an average, not a fixed total.