Answer:
Static friction
Step-by-step explanation:
If the puppies are not moving, there are not dynamic friction or pulling from the puppies. Additionally, the gravity acts toward the center of the Earth and you are trying to move the puppies in an horizontal direction so gravity is not holding her back either.
Finally, The static friction is what is holding her back because it is the force that goes agains the movement, that avoid the initial movement of the puppies.
So, the answer is:
Static friction