The correct answer is A, asking follow-up questions.
When getting group feedback, you shouldn't counter criticism, otherwise why ask for feedback in the first place? The feedback can always be positive or negative.
You don't need to provide extra evidence nor survey the group. Surveying the group could actually impact (positively or negatively) the feedback and you won't get honest answers.
Follow-up questions will give you more precise comments and room for improvement.
