Here's a problem to solve: As humans travel in space, which gas is provided in the atmosphere of the spacecraft and which gas is removed from the atmosphere of the spacecraft?

Among the 4 following options, which is the correct answer?

- A: Oxygen is provided. Carbon dioxide is removed.
 
- B: Carbon dioxide is provided. Oxygen is removed.
 
- C: Carbon dioxide is provided. Nitrogen is removed.
 
- D: Oxygen is provided. Nitrogen is removed.
 