To determine how many people completed graduate school, we can use the percentage given in the table.
According to the table, 25% of the surveyed employees completed graduate school.
Now, we need to calculate 25% of 260 people:
\[ \text{Number of people who completed graduate school} = \frac{25}{100} \times 260 = 0.25 \times 260 = 65 \]
Therefore, 65 people completed graduate school. The correct answer is:
65