Answer:
Letter B is the correct answer.
Explanation:
Letter A is not the correct answer since Emily is not using any evidence and her intention doesn't seem to conclude the discussion.
Even though she synthesized Han's idea, as said in the previous paragraph, Emily doesn't provide one single conclusion, but continues the discussion by ending with a question.
She doesn't bring additional information to support the discussion, and that is why D is also incorrect.
Option B is correct since she challenges established ideas, as she focuses the problem on two things (contamination and the reactors) and then opens the discussion with a new question, as said before.
