Final answer:
Viruses are considered non-living because they lack cells, cannot reproduce independently, and do not have non-membrane bound organelles.
Step-by-step explanation:
A virus is considered non-living because it lacks several characteristics that define living organisms. One of these characteristics is being made of cells, which viruses do not have. Additionally, viruses cannot reproduce on their own and instead depend on a host cell to replicate. Finally, viruses do not have non-membrane bound organelles, further supporting their classification as non-living.