Final answer:
The speed at which the dog was running is 30/b meters per second.
Step-by-step explanation:
To calculate the speed at which the dog was running, we can use the formula:
Speed = Distance / Time
In this case, the distance the dog ran is 30 meters and the time it took is b seconds. Therefore, the speed will be:
Speed = 30 meters / b seconds = 30/b meters per second
So, the correct answer is B) 30/b meters per second.