Answer:
a.tertius gaudens
Step-by-step explanation:
Tertius gaudens also known as rejoicing third is a situation where they are three parties, one party benefits from the conflict between the other two parties. This only works if the three parties have equal and independent relationships among each other.
Since they are three friends, that is Joyce, Holly and Anne, If Holly and Anne are fighting each other, Joyce is going to gain from their conflict since they would spend more time with her. Joyce would be the rejoicing third.