Answer :
#3 A chart showing the significance of three traditional African dances
The evidence that is the best to develop Megan's claim is (3.) A chart showing the significance of three traditional African dances.
Including a chart showing the significance of three traditional African dances would complement Megan's claim because these dances are related to a particular culture and; therefore, to a group of people: the Africans. On the other hand, a study proving that dance is an effective way to lower blood pressure could not help develop Megan's claim since that study focuses more on the health benefits of dancing. Moreover, neither a scientific article explaining the physics needed to achieve balance in ballet nor a map depicting various locations of American ballroom-dance classes would be good evidence for the claim that dance can be used to understand a variety of cultures and people.