An arbiter is consulted when
a. neither side can agree to move forward
b. both groups agree on a compromise
c. a cooperative decision is made
d. someone has their feelings hurt

If you look at the options b) and c) - they are very similar, almost the same! So it is unlikely that only one of them would be correct, either both or none ,so it is none!

An arbiter is asked for help when people can't reach a compromise without him or her - so the correct answer is a)!

Bob: coke is baby pandas.jim: what? how do you figure that coke is baby pandas? bob: because this book says so.jim: how do we know the book is correct? bob: because it says that coke is baby pandas.jim: how does that prove the book's accuracy? bob: because it's statement involving coke and baby pandas is correct, therefore it is accurate.jim: how do we know that it's correct? bob: because we have concluded that the book is accurate, and therefore the statement is correct.therefore, coke is baby pandas.