Final answer:
Natural pollution occurs as a result of natural processes, not human activities, shaping ecosystems.
Explanation:
Natural pollution refers to pollution that occurs as a result of natural processes without human interference. In the given scenarios, the one that would be considered as natural pollution is A melting glacier picks up sediments and deposits them in a lake, causing eutrophication. This process is natural and not caused by direct human activity.
On the other hand, scenarios like a person dumping used motor oil, a maintenance truck leaking coolant, or a person leaving trash next to a garbage can are examples of anthropogenic pollution, which is pollution caused by human activities.
In the context of ecological balance, natural pollution plays a role in shaping ecosystems without direct human intervention.
Learn more about Natural pollution and its distinction from anthropogenic pollution here:
https://brainly.com/question/39442546