There is no natural death in single-celled organisms like Amoeba and bacteria because

1. they can't reproduce sexually

2. they reproduce by binary fission

3. parental body is distributed among the offspring

4. they are microscopic

(c)
There is no natural death in single-celled organisms like Amoeba and bacteria because parental body is distributed among the offspring. In such organisms, reproduction occurs by cell division where a cell (parent) divides into two halves and each rapidly grows into an adult (offspring).