Momentum is calculated using the formula:
\[ \text{Momentum} = \text{mass} \times \text{velocity} \]
Here, the mass of the dog is 10 kg and its velocity is 3 m/s.
Substituting the values into the formula:
\[ \text{Momentum} = 10 , \text{kg} \times 3 , \text{m/s} = 30 , \text{kg*m/s} \]
So the momentum of the dog is 30 kg*m/s.
The correct answer is C. 30 kg*m/s.