Which of the following is an example of a Regulator?

a$.$ A businesswoman breaks off eye contact to signal the end of a meeting.

b$.$ A businesswoman rubs the back of her neck and says "I don't know" during business negotiations.

c$.$ While explaining how to get to the post office; a woman points in the correct direction.

d$.$ When speaking before the boss, an employee nervously rubs his nose.