Answer:
The animals could change it. For example, a bunny could dig a hole in the ground, making a home for other animals inside of it, too, changing the animals' living environment.
Or natural disasters could change their environment, too. For example, if a landslide occurred and covered a pond, frogs and snakes could lose their living areas and food, which would make them have to move to a different area, changing another ecosystem.
I think all of the above...
because I know they built aqueducts and sewers, so since 2 of they are correct, then all 3 must be.
Mutations are disruptions in the human body
A flow of exhaust gasses from a jet engine
No because that would not be your urine
