How can this feedback be improved to make it more
specific?

The most specific answer is A, Revise your claim to make clear to the reader exactly what your position is on global warming.
Have an awesome day! :)
Answer:
The correct answer is letter "A. Revise your claim to make clear to the reader exactly what your position is on global warming".
Explanation:
The best option is letter A because it is very clear that the feedback is advising for reviewing the claim made and what should be reviewed specifically. Feedback should always be clear about what should be reviewed in order to clarify and improve ideas and/or arguments. All the other options advise for reviewing, but they do not point clearly what is necessary for the review.