To find Charlie's running speed, we will use the formula for speed, which is:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]
Given that the distance to the ball is 30 meters and it takes Charlie 13 seconds to get there, we can substitute these values into the formula:
\[ \text{Speed} = \frac{30 \text{ m}}{13 \text{ s}} \approx 2.31 \text{ m/s} \]
Rounding it to one decimal place gives us approximately 2.3 meters per second.
So the correct response is:
2.3 meters per second.