I don’t know why they make everyone type more than 20 characters but B sounds like the most reasonable answer.
A diagram of the sequence of movements or actions of people or things involved in a complex system or activity.
If I am not mistaken, the answer is branch. For example a branch of the military is the U.S Navy.
A peplomer is a glycoprotein spike on a viral capsid or viral envelope. These protrusions will only bind to certain receptors on the host cell; they are essential for both host specificity and viral infectivity.