The correct answer should be "Offer one suggestion at the next meeting".
Explanation:
Constructive criticism always depend on contexts and people envolved. In this case, it should be more constructive to offer an opportunity for the shy person in the meeting to get envolved by making one suggestion, therefore, he/she could feel more confident to participate only once in this first case and then provide more comments and get along with people more and more on the next meetings. All the other options may be constructive, although they may sound rude or not emphatic with the person because they seem more like strict orders with little or no directions and/or help to do so.
