Animals wrestling is a way of learning called
social learning
playing
insightful learning
latent learning

The correct answer for the blank is- playing.

Learning can be described as modification in the behavior of an individual that is acquired through skills, knowledge, and gain of experience.

Wrestling is a playful behavior in animals that is also considered as a way of learning in them. It helps in acquiring skill of battle, which is essential in hunting their prey. This helps them in acquiring various strategies needed for their survival ( such as fighting for obtaining food).

Thus, playing is the right answer.

"d.) carbon dioxide and hydrogen sulfide"