Organisms with the most favourable traits will increase their success rate in a particular environment. Organisms with favorable traits are more likely to reproduce and pass on their traits than organisms without favorable traits, allowing it to survive.
Water-borne diseases, including cholera, typhoid, and dysentery, are caused by drinking water containing infectious viruses or bacteria, which often come from human or animal waste. Water-washed diseases, such as skin and eye infections, are caused by lack of clean water for washing.
The best answer should be
D) Food component that can be stored in the body for future energy needs
I dont think it is symbiotic, it is parasitic relationship. They get blood supply of human and dont give anything useful to humans
