Question

One of the important features of viruses is that, they
A. Occur only inside the bacteria
B. Multiply only in the host cytoplasm
C. Are made up of proteins only
D. Behave as if they were plants

Answer 1

The study of viruses is thought as virology and other people who study viruses are called virologists. Viruses infect and live inside the cells of living organisms. When viruses infect the cells of their host, they will cause disease. Viruses cause AIDS, influenza, chicken pox etc.

Complete step by step answer: A virus could be a sub-microscopic particle which will infect living cells and ranging in size from about 20–300 nm, though some will be larger. Prokaryotes are typically 0.5–5.0 micrometers (µm) long.
An individual virus is named a virion. They are much smaller than a prokaryotic cell. Since viruses don't have cells, they lack cell membranes, cytoplasm, ribosomes, and other cell organelles also. Without these structures, they're unable to create proteins or maybe reproduce on their own and so are dependent on a number cell to synthesize their proteins and to form copies of themselves. Although viruses don't seem to be classified as living things, they share two important traits with living things. They need genetic material, and can evolve.
Characteristics of Viruses
Infectious, acellular pathogens
Obligate intracellular parasites with host and cell-type specificity
DNA or RNA genome (never both)
Genome is surrounded by a protein capsid and, in some cases, a phospholipid membrane studded with viral glycoproteins
Lack genes for several products needed for successful reproduction, requiring exploitation of host-cell genomes to breed
They are non-cellular and extremely simple in structure, consisting mainly of a macromolecule surrounded by a protein envelope called capsid. Therefore, a unit of virus is cited as ‘a virus particle’ instead of ‘a virus cell’.
They are empty, the subtle enzymatic and biosynthetic machinery essential for independent activities of cellular life. Therefore, they'll grow only inside suitable living cells. That's why; they're cultivated within the laboratory only inside living cells, unlike bacteria and fungi, which may be cultivated within the laboratory on non-living matter like culture medium.
They are ultra-microscopic and might only be visualized under a microscope.
They are not increasing in size.
They'll meet up with filters, through which bacteria cannot pass.
A virulent disease is termed either ‘DNA virus’ or ‘RNA virus’ counting on whether it contains the macromolecule DNA or RNA.

Note: Viruses may also possess additional components, with the foremost common being a further membranous layer that surrounds the nucleocapsid, called an envelope. The envelope is really acquired from the nuclear or cell membrane of the infected host cell, and so modified with viral proteins called peplomers.