Are chemosynthetic bacteria-autotrophic or heterotrophic?

How is the five–kingdom classification advantageous over the two kingdom classification?

Polluted water bodies have usually very high abundance of plants like Nostoc and Oscillitoria. Give reasons.

The common name of pea is simpler than its botanical (scientific) name Pisum sativum. Why then is the simpler common name not used instead of the complex scientific/ botanical name in biology?

A virus is considered as a living organism and an obligate parasite when inside a host cell. But virus is not classified along with bacteria or fungi. What are the characters of virus that are similar to non-living objects?