SORU: aşağıdaki parçaya göre cevaplayınız
According to the passage, ----.
Humans have evolved to work best in the atmosphere
and gravity that exist on the Earth’s surface. To survive
in space, astronauts have to take an Earth-like
environment with them such as fresh oxygen, which is
circulated around the craft for them to breathe. The
main difference in space is the weightlessness causing
astronauts to float around. As soon as astronauts go
into space, their bodies start adapting to this
weightlessness. Muscles, bones, heart and blood all
undergo changes. At least half of all astronauts suffer
an unpleasant reaction to weightlessness. On the Earth,
gravity exerts a force on our bodies, which gives us
weight and keeps us rooted to the ground. It also pulls
body fluid downwards. In space, astronauts lose their
sense of balance. They can feel sick, and go off their
food. It can take two weeks for the digestive system to
fully adjust. Therefore, NASA plans no spacewalks
during the first three days of a mission, because an
astronaut who vomits inside a spacesuit risks
suffocation.