阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。
A
Life on the ISS
Ø Waking up
Mission control wakes the crew up by turning on the lights at 6 a.m. The day starts the same as it would on Earth. While you wet your brush with water that will stick to its bristles (刷毛), the toothbrush and the tube of toothpaste can be left to float in the air, which is rarely seen on earth. After breakfast, the crew calls down to mission control for a planning conference to run through the day’s schedule.
Ø Maintenance
Then it is time for household chores. Most days, the ISS requires routine maintenance and safety checks. One day it might be moving some supplies; another day could involve repairing an essential piece of equipment.
Ø A visit to the gym
One of the main aims of the ISS is to discover how weightlessness affects the human body. Astronauts lose muscle strength in space and are more likely to break their bones once they return to Earth. To slow this process down, each crew member is required to exercise for at least two hours a day.
Ø Mealtimes
Food comes in several forms. Dehydrated (脱水的) meals come in small bags, and spices are also available, just like on the table back home. But salt and pepper have been transformed into liquids.
Ø Experiments
Each astronaut spends part of their day on experiments in the labs on the ISS, so that scientists back on Earth can better understand how the conditions in space affect things. Mice, ants, fish and worms have all been sent to the station to see how zero-gravity affects their bodies and behavior.
Ø Free time
Once the crew has finished their scheduled tasks for the day, they are free to spend any remaining time they have left from their evening. Perhaps the most popular pastime is to simply watch the Earth spinning silently below the station.
21. According to the article, ISS astronauts’ daily routine is different from ours on Earth in terms of the way they _____.
A. work out B. having their meals
C. brush their teeth D. do household chores
22. According to the article, astronauts are NOT allowed to _____ on the ISS.
A. do experiments on animals B. have pepper with their food
C. decide their own work schedules D. carry out routine maintenance alone
23. What can we learn from the article?
A. The ISS acts as a scientific research lab in outer space.
B. Mission control is of little importance to the success of a space mission.
C. In the long term, zero-gravity has no negative effect on the human body.
D. Astronauts rarely watch the Earth from the ISS for fear of getting homesick.
