Here's a problem to solve: Why is it difficult to create a terrarium ecosystem that will last a long time without human help?

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

- A: Terrarium ecosystems cannot get enough sunlight.
 
- B: Terrarium ecosystems cannot get enough oxygen.
 
- C: Ecosystems with few species are weak and unstable.
 
- D: All ecosystems require thoughtful human management.
 