which of the following is not a solution to protect the water in the two wells in danger of becoming contaminated?

The correct option is C. Building a well between the two wells that goes deeper into the earth would not stop the water from being polluted .

Explanation:

Even if a well was constructed between the wells B and C, it wouldn't have stopped the contamination of the water. As the oil would still be leaking and it would contaminate the wells.

All of the other options can be used to stop the contamination.

Option A suggests building an impermeable membrane that would stop the oil flow. Hence, the water in the wells will not be contaminated.

Option B suggests not using the water from the wells and using an alternate water supply. The alternate water supply wouldn't be contaminated with oil.

Option D suggests chemically purifying the contaminated water. This can be an effective technique to clean the contaminated water.  

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.