If one defines life as the simplest form capable of displaying the most essential attributes of a living thing, one very quickly realizes that the only real criterion for life is the ability to replicate. Only systems that contain nucleic acids are capable of this phenomenon. This sort of reasoning has led to a new definition of organism: An organism is the unit element of a continuous lineage with an individual evolutionary history. Considering the new definition of life, all but one piece evidence supports the fact that a virus must be referred to as an organism. That is: A) Viruses contain nucleic acids. B) Viruses are capable of replication. C) Viruses have a simple cellular structure. D) Viruses have an evolutionary history and that implies lineage.

Viruses are a microorganism that contains nucleic acids and therefore are can replicate and create a lineage. This according to new definitions of life make viruses living organisms as the text defines "the only real criterion for life is the ability to replicate" which is accomplished by viruses. However, that viruses have a simple cellular structure is not a piece of evidence that supports the idea they are living organism, as simple or complex structures do not define life but this is only defined by the ability to replicate or form lineage and therefore contain nucleic acids. Thus the correct option is C.