The toxic runoff from the farms will directly enters the water bodies of the earth through the drainage system.
The emissions from the cars will go into atmosphere and will react with water and then it will enter the earth's water. So, it is not directly affecting the earth's water.
The dumping trash on roadsides do not enter the earth's water. It can enter the earth's water through rains.
The production of oxygen by trees is not pollution.
Hence, option (A) is correct.