Question

in 2021, tardigrades took up residence on the international space station—this time, on the inside of the spacecraft. the purpose was to allow scientists to study specific ways in which tardigrades adapt to space - flight conditions over time. the information scientists gather about tardigrades in space may one day enable humans to extend our reach into the vast universe.
what is the text mainly about?
it is about how being tiny makes it easier for tardigrades to survive in the deep ocean.
it is about how tiny tardigrades can threaten the survival of much larger animals.
it is about how astronauts now use tiny tardigrades to help them survive in space.
it is about how tiny creatures called tardigrades have amazing survival abilities.

Explanation:

The text talks about tardigrades living on the International Space Station in 2021 so scientists can study their adaptation to space - flight conditions, which relates to their amazing survival abilities (since they can adapt to space conditions). The first option is about deep ocean, which is not in the text. The second option is about threatening larger animals, not mentioned. The third option says astronauts use them to survive, but the text is about studying them for human space exploration, not using them for astronaut survival. So the correct option is the one about tardigrades' amazing survival abilities.

Answer:

It is about how tiny creatures called tardigrades have amazing survival abilities.