The scenario you described suggests that the animal learned from previous experience. This is indicative of problem-solving ability, as the animal would likely need to remember which strings it had already pulled and the outcomes of those actions to optimize its chances of success in obtaining food. Therefore, the most accurate interpretation would be:
3. The animal learned from previous experience.
This demonstrates that the animal is capable of engaging in trial-and-error learning, which is a fundamental aspect of problem solving in many species.