What could be a change that happens upstream that could affect the rest of the ecosystem

Pollution upstream (on a river) could poison many animals in the area, as they drink the polluted water which is not safe for them.

The answer is d) rift

Unique question.well, using science, you cannot create or destroy even if you do eat yourself so you would not grow twice as big, nor would you disappear. you would stay the same but change states potentially, or at least change your appearance (obviously).hope this . keep up these unique questions.