Final answer:
The thick film of algae on the body of water was most likely caused by the runoff of fertilizers from local farms, excessive sunlight, and the presence of pollutants in the water. The correct option is 1) Runoff of fertilizers from local farms
Step-by-step explanation:
The thick film of algae on the body of water was most likely caused by the runoff of fertilizers from local farms. When fertilizers are washed into bodies of water through runoff, they introduce excess nutrients like nitrogen and phosphorus. These nutrients promote the growth of algae, leading to algal blooms. The algae consume oxygen, making it difficult for other aquatic organisms to survive.
Excessive sunlight can also contribute to the growth of algae. Sunlight provides the energy needed for photosynthesis, which is how algae produce food. When there is an abundance of sunlight, algae can grow rapidly.
The presence of pollutants in the water can also contribute to the growth of algae. Pollutants, such as organic matter and chemicals from sewage and farm animal waste, can provide additional nutrients for algae to thrive. The correct option is 1) Runoff of fertilizers from local farms