number of fish. depth of the lake. quality of the water. speed of the water.
I gave my students this multiple choice question: Scientists go to a lake once a month to take samples of water. They are most likely studying the

Only one answer is correct among these 4 choices:
- number of fish.
- depth of the lake.
- quality of the water.
- speed of the water.

Could you tell me which one is correct?

quality of the water.