Answer:
Poaching.
Step-by-step explanation:
The descriptions for each of the terms you listed:
- poaching: illegal hunting of wild animals
- habitat destruction: the process in which a habitat becomes unsuitable for supporting life, often by human activity
- pollution: the introduction of hazardous or harmful waste into the environment
- nonnative species: a species introduced to a new habitat, often by human activity, that thrives unusually well due to having no natural predators in its new habitat.
Hunting elephants (an illegal activity in many countries) for their ivory is considered poaching.