Which incident command system element provides a command structure to enable agencies with different legal, jurisdictional, and functional responsibilities to coordinate, plan, and interact effectively on scene while maintaining their own authority, responsibility, and accountability?
a. unified command
b. area command
c. unity of command
d. unity of effort

The Incident Command System element that provides a command structure to enable agencies with different legal, jurisdictional, and functional
responsibilities to coordinate, plan, and interact effectively on scene while maintaining their own authority, responsibility, and accountability would be a "Unified Command," since in this case all agencies are "unified" in order to achieve a common goal. 

Interpreting the results of his experiment : )