阅读下面短文，从短文后各题所给的A、B、C和D四个选项中，故答案选出可以填入空白处的最佳选项。
Chinese volunteers have completed a one-year test living in a simulated（模拟的）space lab in Beijing. The total length of the test, which started on May 10th last year, 1 370 days, thus setting a new record for the 2 stay in a simulated space lab.
The space lab, called the Yuegong-1, or Lunar Palace 1, measures around 150 square meters. It 3 four sleeping rooms, a bathroom, a waste-treatment room and a room for raising animals. The Yuegong-1 provides everything humans need to survive in an environment 4 to that of a space station in outer space. Oxygen, water and food are 5 within it.
A total of eight 6, all of whom are students at Beihang University, took turns 7 in the space lab. They were divided into 8 groups. On May 10, 2017, two men and two women 9 the Yuegong-1 for an initial （最初的）stay of 60 days. On July 9, they were 10 by another group of four, who stayed 200 days. The second group of students 11 on January 26, 2018, and the initial group12 and spent 110 days inside it.
13, the volunteers were expected to stay in the Yuegong-1 for 365 days. But the project ended up 14370 days —from May 10 last year until May 15. The 15 five days were designed as a way to simulate a（n）16, in which the spaceship might experience a 17 in returning to earth.
The goal of the project “Yuegong 365” is to 18 the limits of humans' ability to live in a 19 ecosystem for China's manned moon landing ambition. The success of the project means that China goes one step closer to putting 20 on the moon.
