It shows the doer of the action.It comes before verb and indicates this action or work is done by it/him/her etc.Ex.Susan switched off the lights. Who switched off the lights? The answer is Susan (subject of the sentence)
Answer:
To swear an oath of brotherhood
Explanation:
The three rioters swore an oath to kill death but greed took a tow on them and they ended up killing each other because of eight bushels of gold they each wanted for their vices.
I would say a) joy but i’m not a 100% sure