阅读下面短文,从所给选项中选出能填入空白处的最佳选项,使短文通顺,结构完整,其中有一项是多余选项。
April 24 is a special day, Space Day of China. It is honoured to celebrate the country's development in space exploration. The manned space missions are a big part of it. (1)
What problems do astronauts meet?
Astronauts may face many challenges in space. There is low gravity there, which affects their bodies. (2) What's more, if something goes wrong on their mission all of a sudden, they have to work out how to fix it under huge pressure. That's why astronauts have to be smart, strong, and ready for any challenge before they can go to space.
(3)
"To make sure that Chinese astronauts complete their missions and return to the earth safely, over 200 kinds of training are set," said Huang Weifen, chief designer of the project. (4) So before astronauts can go to space, they train like this for at least three and a half years.
(5) This helps them get ready for the weightless environment in space. Huang explained that astronauts wear diving suits(潜水服) that weigh more than 100 kilograms and stay underwater for six hours at a time. She said that it was quite hard. For example, Nie Haisheng even lost 2 kilos after an underwater training.
A. How are astronauts trained?
B. What is the weightless feeling?
C. Being an astronaut is exciting but difficult.
D. One of the hardest parts of the training is the underwater training.
E. Also, staying long in a tiny spaceship can make them feel stressed out.
F. These include not only physical training but also some basic science training.