d) Swimming in the pond
Swimming in the pond will produce the least pollution of water because no harmful pollutants or any chemicals would be involved in the process.
- Washing of clothes would release the soap and detergent being used in to the water.
- Animals might be covered with dust and excreta which when they bathe will get washed in the water of the pond.
- Washing motor vehicles too would cause pollution because motor vehicles produce soot and other harmful particles which will get washed in the water.