Final answer:
The different organisms a virus can infect define its host range. This range can be narrow, limited to one or a few species, or broad, encompassing multiple species. Specific interactions with host cell receptors determine the host range and tissue tropism of the virus.
Step-by-step explanation:
The different organisms a virus can infect indicate the host range of the virus. The correct answer is A) Host range. A virus's host range can be quite narrow, meaning it can only infect cells from one or just a few species. Alternatively, some viruses have a broad host range and can infect multiple species. The host range is determined by the virus's ability to bind to receptor sites on the host cell membrane through specific proteins in the capsid or glycoproteins in the viral envelope. This specificity restricts the virus to certain hosts and even to certain cells within those hosts, which is also referred to as tissue tropism.