A) It stayed in the air for about two hours. B) It took off and landed on a football field. C) It proved to be of high commercial value. D) It made a series of sharp turns in the sky. 6. A) Engineering problems. B) The air pollution it produced. C) Inadequate funding. D) The opposition from the military. 7. A) It uses the latest aviation technology. B) It flies faster than a commercial jet. C) It is a safer means of transportation. D) It is more environmentally friendly.