一道BIBLE上的reasoning。求助解释！！谢谢！！！！

lihaolan

psychologist:the obligation to express gratitude cannot be fulfilled anonymouusly.However much society may have changed over the centuries, human psychology is still driven primarily by personal interaction. thus ,the important social function of positively reinforcing those behaviors that have benificial consequences for others can be served on if the benefactor knows the source of the gratitude.
which one of the following most accurately describes the role played in psychologist's argument by the claim that the obligation to express gratitude cannot be fulfilled anonymously?
A it is an illustration of premise that might support the argument's concluson
B it is used to counter a consideration that might be taken to undermine the argument's conclusion
C it is used to support indirectly a claim that the argument in turn used to support directly the conclusion
D it is used to identify the social benefit with which the argument is concerned
E it is the conclusion that the argument is intended to support。
key E
求助。为什么是结论。文章不是HOWEVER THUS 么。。。具体的内容有什么逻辑支持也没有读懂！！求助解释下！！

lihaolan

however在这里就不是转折了是么。。第一句和第二句有对比转折么。。