Passage Summary: A scientist suggests that dinosaurs didn't start flying by running and jumping; instead, they probably lived in trees and glided down, because the simple wings they had early on were better suited for gliding than for ground takeoffs.

Conclusion: The first dinosaurs to fly likely transitioned to flight by gliding from trees rather than taking off from the ground.

Reasoning: Gliding is possible with simple wings, and these simple structures represent the necessary evolutionary steps toward the complex wings seen in later dinosaurs.

Analysis: This is a 'Strengthen EXCEPT' question, which means four of the answers will support the 'tree-down' theory and one will not. The scientist's argument relies on an evolutionary progression where simple wings are functionally sufficient for gliding but perhaps not for the more strenuous task of ground-based liftoff. To strengthen this, we would look for evidence that early dinosaurs lived in trees or that ground-based flight requires more advanced anatomy than they possessed. The 'except' answer might be irrelevant or could even provide support for the rival 'ground-up' theory.