阅读下面短文, 从短文后的选项中选出可以填入空白处的最佳选项。选项中有两项为多余选项。
Hotels orbit Saturn's pale orange moon,Titan. Cruise ships roam the docking stations like fish. Have you ever imagined making this future space travel in the fiction films a reality?
Large companies and entire governments have teamed up to make space travel and exploration easier and quicker. Several countries are planning space missions between now and 2025. Some aim to build stations orbiting the moon. Eventually, they maybe build settlements there!
Yet no human has traveled beyond Earth's orbit since 1972. Money is part of the problem. To put a pound of anything in space costs about $10,000. Consider that the old NASA space shuttles carried 2. 2 million pounds (998,000 kg) of fuel alone. Once in space, we face the problem of enormous space. Current technology and fuels can propel spacecraft at around 36,000 miles (58,000 km) per hour. Therefore, Human astronauts need some sort of new engine technology. Without it, they would not likely live long enough to complete journeys to other worlds.
Some human astronauts live and work in the International Space Station(ISS). They're in small spaces far from home. They suffer mentally and emotionally. Moods sour. Depression kicks in. Clear thinking muddies. Fear runs high.
Accessing fresh food is another issue. Today, astronauts eat lots of freeze-dried meals.
We need those to be healthy. Of course, space doesn't have grocery stores. Deep-space travelers may need to grow food on board. Unfortunately, good nutrition cannot fully protect an astronaut. All that time spent floating affects bones, muscles, and the blood. The body suffers damage from radiation streaming from stars and supernovas.
A. Others intend to land humans on Mars.
B. Freezing food reduces its vitamins and minerals.
C. Even if a trip fit within a lifetime, it wouldn't be easy.
D. In some ways, we are on the edge of this imagined future.
E. Frozen food cannot provide them with enough good nutrition.
F. With that amazing speed, spacecrafts would carry astronauts to other worlds.
G. Even at that speed, it would take 78,000 years to reach the nearest star system.