Answer:a. Tell a joke
Explanation:Some people or cultures consider certain jokes to be very offensive and some people don't really take a joke as well as you may hope they would especially if they came for a speech , they may be too formal to open to a joke and it may create an awkward atmosphere before you even start. It would be good to get to know the overall background of your audience so that even if you make a joke it would be an appropriate one based on your audience.