Unlike the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries, a permanently orbiting space station will have to generate its own electricity.

• Athe short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries  
• Bthe shuttle and earlier spacecraft, with sufficient enough power in fuel cells and batteries for their short flights  
• Cthe short flights of the shuttle and earlier spacecraft, which enabled them to carry sufficient enough power in fuel cells and batteries  
• Dthe shuttle and earlier spacecraft, which were capable of carrying sufficient power in fuel cells and batteries for their short flights  
• Ethe flights of the shuttle and earlier spacecraft, whose shortness allowed them to carry sufficient power in fuel cells and batteries