Final answer:
A nonliving particle reliant on a host cell for survival is called a virus, which is a noncellular entity unable to grow or reproduce without infecting a host.
Step-by-step explanation:
A nonliving particle that is completely reliant on the host cell for survival is called a virus. Option A) Virus is the correct answer. Viruses are noncellular parasitic entities that cannot be classified within any kingdom and exist between living organisms and nonliving entities. They contain genetic material and can evolve but cannot grow, metabolize, or reproduce without a host. Viruses infect various hosts, such as bacteria, plants, and animals, to replicate and produce more virus particles, known as virions.
Option B) Bacteriophage is a type of virus that specifically infects bacteria. Option C) Prion is an infectious agent composed of protein in a misfolded form, which is also reliant on a host but different from a virus. Option D) Viroid is a small infectious pathogen composed of RNA, also not synonymous with a virus. Therefore, when referring to a nonliving particle that relies on a host cell to survive, we designate it as a virus.
A virus is a nonliving particle that is completely reliant on a host cell for survival. Viruses lack cell organelles and cannot perform protein synthesis or reproduce on their own. They must infect a host cell and use the host cell's resources to replicate.