Philosopher: Philosophers usually treat emotions as nonrational.
Conclusion
Emotion is not nonrational.
Intermediate Conclusion
Emotion only seems nonrational way because language lacks the ability to convey adequate conceptions of emotion.
Evidence
The words we use to refer to emotions name only very general kinds of inner experience, such as excitement / calm / joy, but there is no language for describing just how one joy differs from another.
Evaluate
Whenever we do Main Conclusion / Role, we listen for Rebuttal/Pivot conclusions (most of them are that style) or First Sentence conclusions (the 2nd most common style).
Since this paragraph begins with an Attribution, "Philosophers usually think of emotions as X", we'd be waiting for a Pivot + Pushback, and so when we see "But emotion is not nonrational", we most likely have our rebuttal conclusion.
Everything after that is support for the main conclusion.
They're asking us about the last sentence, which is hella confusing because it's prefaced by Thus (which usually indicates conclusion) and by "for example" (which always indicates support).
How can the last claim be a conclusion and a premise?!
We need to remember that premise/conclusion indicator words can also be used to indicate Cause/Effect. /
That's why we see a Thus in front of this supporting idea. The previous sentence causes this last claim to be true. The fact that we have words for only general emotional states is why we don't have specific words for different types of joy.
Goal
We know this final claim plays a supporting role, and we know that the main conclusion is "Emotion is not nonrational", that's good enough to head to the answers.