Question

Why are viruses considered to be non-living?
A. They do not have cells.
B. They cannot reproduce on their own.
C. They have no metabolic activity.
D. All of the above.

Answer 1

Hint: Outside the host cell virus behaves like matter. Only upon finding a living host organism, it injects its DNA/RNA to propagate its genes.

Complete answer: Virus is an infectious agent and quite small.
It injects its genetic material into the host and replicates within the living cells of the host.
A virus is made up of just genetic material, be it DNA or RNA.
The genetic material is covered by a protein-made capsule, often called a capsid.
The virus first attaches to the surface of bacteria.
It occurs by random encounters; then it injects genetic material through the host cell membrane.
The protein coat remains outside of the host cell.
After injecting viral DNA, the normal mode of replication and transcription does not occur in the host cell.
Rather, the host cell now produces viral DNA and its proteins.
Hence, it has no cell and metabolic activity and it cannot reproduce on its own.
 

So, the correct option is D. All of the above.

Note: The entire virus is called a virion and it consists of both the outer capsid shell and the inner nucleic acid component. The capsid provides specificity of the virus while the nucleic acid is the cause of its infectivity.