The correct option is D The virus must have a particular shape that will match up with the proteins on the surface of the host cell.
Viruses are organisms that survive in living hosts. These are actually biological agents that produce identical copies of its strain inside the host cell and leads to infections. Viruses are found in the environment and upon the presence of a host cell will try to attack. However, in order to attack, the virus must attach to a host cell which can be achieved when receptors on the viral envelope become connected to complementary receptor proteins of the target cells membrane. Thus, the correct answer is option D.