At OB$,$ Inc., you have been elected as chair of the volunteer committee. Each year, OB$,$ Inc. encourages its employees to participate in one company$-$wide volunteer opportunity. This year, the volunteer opportunity is a blood drive to help out the local hospital. You request that each employee who wishes to participate sign up for a specific day and time because you know that once people have a specific day and time scheduled, they are more likely to show up$.$ The persuasion principle that applies most appropriately to this situation is

a$.$

scarcity.

b$.$

liking.

c$.$

social proof.

d$.$

consistency.

e$.$

authority.