Final answer:
Dogs cannot catch measles from humans because the measles virus is species-specific and dogs lack the receptors needed for the virus to attach to and infect their cells.
Step-by-step explanation:
The reason that dogs don't catch the measles from humans is most accurately described by option b) Measles is species-specific. This means that the measles virus is adapted to infect specific species. Different species have different cell receptors, which viruses must attach to in order to enter and infect the cell. The measles virus specifically recognises and binds to receptors that are present on human cells, but these receptors are not found on dog cells. As a consequence, even if a dog were to be exposed to the measles virus, the virus could not attach to and infect the dog's cells because it cannot find the appropriate receptors.
Additionally, viruses tend to co-evolve with their host species and consequently, they evolve mechanisms that allow them to evade or manipulate the host's immune system to their advantage. However, these mechanisms are often species-specific, contributing to the inability of many viruses to jump across species barriers. This underlies the concept expressed by option c) Dogs lack the receptors for measles virus and contributes to the species-specific nature of many viral infections.