decrease the temperature of the factory water increase the temperature of the river water remove the vegetation from the river add more fish to the river
I gave my students this multiple choice question: Water used in a factory is heated to 75 degrees Celsius. It is discharged into a nearby river that has a normal temperature of 20 degrees Celsius. Which should most likely be done to minimize damage to the river?

Only one answer is correct among these 4 choices:
- decrease the temperature of the factory water
- increase the temperature of the river water
- remove the vegetation from the river
- add more fish to the river

Could you tell me which one is correct?

decrease the temperature of the factory water