Which of the following statements about viruses is false?

A) They are obligate intracellular pathogens.

B) CTLs and NK cells provide protective immune effector functions.

C) They are very small uni-cellular microorgansisms.

D) They are generally visible only by electron microscope.

C) They are very small uni-cellular microorganisms.

Explanation:

Microorganisms are very small organisms which are not visible to naked eyes. They include bacteria, some protists, some fungi etc. Viruses are also very small pathogens which can infect all types of living organisms, from plants to animals to bacteria.

Viruses are traditionally not considered microorganisms because they behave like non living entities outside the host cell. They do not have a proper cellular structure. Most of them just have genetic material enclosed in a protein shell. They do not even perform normal metabolic functions like replication outside the hosts's body. Hence, they are not considered microorganisms.