Expert pool players were observed to make 71 percent of their shots when alone. when four people watched them, they made 80 percent of their shots. this best illustrates what?

social facilitation

Explanation:

social facilitation refers to a situation when a certain individual's performance is heavily affected by the presence of audience. (The effect could be either positive or negative).

For some people, the presence of audiences release various type of chemicals in their brain that help them to be more focus and able to do a better performance.

d.) continue to rise rapidly