To find the unit rate from the graph, we can use the coordinates of the point given, which is (100, 20).
Here, the x-coordinate (100) represents the amount of punch in fluid ounces, and the y-coordinate (20) represents the number of servings.
To find the unit rate (the amount of punch per serving), we can calculate it as follows:
\[ \text{Unit Rate} = \frac{\text{Amount of Punch (fluid ounces)}}{\text{Number of Servings}} = \frac{100 \text{ fluid ounces}}{20 \text{ servings}} \]
Calculating this gives:
\[ \text{Unit Rate} = \frac{100}{20} = 5 \text{ fluid ounces per serving} \]
Therefore, the correct answer is:
C. 5 fluid ounces per serving.