Answer:
foot-in-the door technique
Step-by-step explanation:
The foot-in-the door technique assumes the agreement to smaller request increases the likelihood or the chances of agreement to another request, larger than the previous request.
So, in the initial stage, a small request is made and the agreement of the person to this it becomes harder for them refusing a greater request.
Thus, In case of Jenna, she initially agreed for volunteering the work of cleaning of the beach and after the request for a greater work was made to her for her she agreed to it.