It will put acid into the lakes and ponds. It will begin the process of building soil. It will prevent the carbon cycle from occurring. It will prevent bacteria from invading the ecosystem.
I gave my students this multiple choice question: A glacier retreats leaving bare rocks. Lichens begin to live on the rocks. The lichens produce an acid that starts to break down the rocks. How will this process affect the environment?

Only one answer is correct among these 4 choices:
- It will put acid into the lakes and ponds.
- It will begin the process of building soil.
- It will prevent the carbon cycle from occurring.
- It will prevent bacteria from invading the ecosystem.

Could you tell me which one is correct?

It will begin the process of building soil.