Name the group of viruses responsible for causing AIDS in humans. Why are these viruses so named?

Name the bacterium responsible for peptic ulcer.

Name the organism responsible for filarial disease.

Name the living beings responsible for biodiversity?

Name four groups of Etherians.

Name the enzyme responsible for nitrogen reduction.

Name the hormone responsible for the descent of testes into the scrotum. Why does the failure of the process result in sterlity ?