The most appropriate research question for the team of engineers testing different angles for the blades of the wind turbine would be:
Which angle converts the largest percentage of kinetic energy from the wind into potential energy of the turbine?
This is because wind energy is primarily kinetic energy, and the goal of the wind turbine is to convert that kinetic energy into mechanical energy (movement) which can then be transformed into electrical energy. The research focuses on optimizing the blade angle to maximize this conversion efficiency.