The coach could grade their performance.
Social loafing refers to the fact that a person might not produce much effort when in a group, as opposed when alone. So, these kids know that together they are pretty good, so they don't have to try hard; but when they are alone, they do. In order to prevent this, the coach might want to grade their performance, because then they will try harder.
I have read but what is it about?
the answer is D. eeeeeeeeeeeeeeeeeeeeee
a. stimulus
Stimulus is something that can evoke a physiological response, it can be in or external.
