the answer is C you can argue both about that
For he thinks that this kind of friendship can exist only when one spends a great deal of time with the other person, participating in joint activities and engaging in mutually beneficial behavior; and one cannot cooperate on these close terms with every member of the political community.
I believe the answer is "not credible."
Hope this helped! =)
Sentiences 3 and 8 because they express emotional thought other than fact. For sentence three, using "terrible waste" can be debateable and shows more of an opinion. And sentence 8, by using "shouldn't" showing its still a posssiby something can or can not happen.