Final answer:
True, viruses must enter a host cell to obtain the necessary nutrients for replication. They are obligate intracellular parasites that use the host cell's machinery for the production of viral components and lead to the release of new virus particles.
Step-by-step explanation:
When a virus invades the body, it must enter a host cell to obtain nutrients necessary to replicate. The correct answer is A. True. Viruses are obligate intracellular parasites which means they must invade and take over a host cell to replicate and produce offspring. They achieve this by attaching to and entering permissive host cells. Once inside, they use the host cell's machinery to synthesize viral proteins and copy their genome, eventually leading to the release of new virions that can infect additional cells. During this process, the host cell can undergo cytopathic effects, which may result in cell damage or death. Viruses enter cells through various mechanisms, such as receptor-mediated endocytosis or fusion with the cell membrane. These methods involve the virus attaching to a specific receptor site on the host cell. This specificity is due to the presence of viral receptors on the cell surface, which are required for the virus to attach and gain entry. The interaction between viral particles and host cells is complex and relies on many factors, including the virus's ability to evade immune responses and cellular conditions that allow for viral replication.