to help astronauts breathe in outer space to help with the weight of astronauts during space walks to manage carbon dioxide that astronauts breathe out to mix with the thin atmosphere for astronauts during space walks
I gave my students this multiple choice question: Why do astronauts need oxygen in the backpacks of their spacesuits?

Only one answer is correct among these 4 choices:
- to help astronauts breathe in outer space
- to help with the weight of astronauts during space walks
- to manage carbon dioxide that astronauts breathe out
- to mix with the thin atmosphere for astronauts during space walks

Could you tell me which one is correct?

to help astronauts breathe in outer space