400
What is the topic sentence of this paragraph?
And yet, Linenger recovered quickly. In fact, almost two dozen astronauts have lived in space for more than six months, and four have stayed in orbit for more than a year. These men and women faced the discomforts of weightlessness and overcame them. And they all readapted to Earth’s gravity without problems, proving that voyages to Mars are possible….Even if it feels like you are hanging upside down the whole time!
In fact, almost two dozen astronauts...