At the school track meet, Dita ran 100 meters at a rate of 6.25 meters per second.

To find out how long it took Dita to finish the race, we can use the formula:

\[ t = \frac{d}{r} \]

where:
- \( d \) is the distance (100 meters),
- \( r \) is the rate (6.25 meters per second).

Substituting the values:

\[ t = \frac{100 \text{ meters}}{6.25 \text{ meters/second}} \]

Calculating this gives:

\[ t = \frac{100}{6.25} = 16 \text{ seconds} \]

Therefore, the time it took Dita to finish the race is **A. 16 seconds**.