Adults have the right to vote; so should adolescents.
Conclusion (should = opinion)
Adolescents should have the right to vote.
Evidence
Adults have the right to vote, and to the extend that adolescents and adults are different, adults can't be expected to represent the interests of adolescents.
If they can't represent the interests of adolescents, then only by giving adolescents the vote will these interests be represented.
Evaluate
There are a lot of flaws with this argument, but we don't care since we're just doing Role.
We know when we do Role or Main Conclusion that most of the time the main conclusion will be found in the first sentence or in some pivot/rebuttal moments.
Here we have the conclusion in the first sentence, and then the paragraph goes on to try to convince us that adolescents should have the right to vote.
But we're being asked about the second sentence, which was a Counterpoint, an Opposing Idea, a concession that the author is making to her potential opponents.
Concession language is like, Admittedly, X While it is true that X Granted, X Naturally, X is true.
Concessions get followed by pivots (unless they're set up with a word that signals a pivot, like "although / while / despite").
Here the 2nd sentence is followed by the pivot But and then the author begins her supporting ideas for the conclusion that adolescents should have the right to vote.
Goal
We're looking for something like, a potential objection a concession an acknowledgment of an opposing point