Final answer:
When a prospect expresses doubt concerning product claims, it is important to address their concerns by asking for more details and then addressing them.
Step-by-step explanation:
When a prospect expresses doubt concerning product claims you make, it is important to address their concerns in a professional and friendly manner. The most appropriate course of action would be to ask for more details about their doubts and then address them. This allows you to understand the specific concerns they have and provide relevant information or evidence to reassure them.