Answer:
b) Thank the representative and accept the offer to cover expenses of your participation.
Step-by-step explanation:
Since the representative asked for your participation on an expert panel that will be held at an upcoming international professional conference. The representative offered to pay for travel and lodgings for you and a guest to the conference.
The response that be most effective for helping you to make an ethical decision is to first of all, thank the representative and accept the offer to cover expenses of your participation.
As a sign of gratitude, you should thank them for the honor and privilege bestowed on you to be a part of the panel.
Also, having them offering to pay your travel and lodging costs would help you channel your energy into preparing and equipping yourself with necessary information and knowledge about the conference.