Final answer:
According to cell doctrine, viruses are not considered living because they lack cells, cannot maintain homeostasis, and cannot reproduce or carry out biological processes independently of a host.
Step-by-step explanation:
Viruses are often a topic of debate when it comes to their classification as living or non-living entities. According to cell theory, which posits that all living organisms are made up of cells, viruses do not qualify as living because they are acellular - meaning they lack cells entirely. Furthermore, viruses are incapable of reproducing independently or maintaining homeostasis without a host. They are essentially DNA or RNA encapsulated within a protein coat and require a host cell to carry out any kind of replication. This obligate parasitic nature sets them apart from living organisms that possess cellular machinery and metabolic processes. However, it is important to note that viruses do have genetic material and can evolve, which has led to confusion about their classification.
In summary, the answer to the question of whether viruses are considered living according to cell doctrine is 'b) No'. They are not made of cells, cannot maintain homeostasis on their own, and cannot independently perform biological processes that are characteristic of life.