To calculate the z-score for a data point, you can use the formula:
\[ z = \frac{(X - \mu)}{\sigma} \]
where:
- \( X \) is the data point (in this case, 10),
- \( \mu \) is the mean (in this case, 5),
- \( \sigma \) is the standard deviation (in this case, 2).
Now, plug in the values:
\[ z = \frac{(10 - 5)}{2} = \frac{5}{2} = 2.5 \]
Thus, the z-score is 2.5.
So the correct answer is 2.5.