Which has the highest density, water at 0c, water at 4c, water at 6c, water at 8c

water at 0C

Explanation:

The colder the water is, the denser it is, so the water here with the lowest temperature, is 0C

it is important to conserve water because there is very limited amount of freshwater here on earth and if we are not smart about how we use it we will only be runnning out of our supply faster than neccessarry.