1. Some dinosaurs could both fly and walk. However, did they originally fly and then learn to walk, or did they originally walk and then learn to fly? By saying that flying was an evolutionary advantage conferred upon them, the author is implying that the latter is true: first, the dinosaurs walked, and then they learned to fly.

2. The author states that computer simulations showed that the pteranodon was able to walk. This fact is then assumed to be true for the rest of the passage, which attempts to explain why they walked. Hence, the computer simulation was enough evidence to conclude that the pteranodon did indeed walk. Statement I is true.

The passage tries to explain why the pteranodon walked, but it does not explain how it walked, other than to say that it retracted its wrists. We aren't give any other adaptations, so II is not right.

The theory that pteranodons learned to walk in order to forage for food on the ground was "enticing," or compelling. However, even though it is compelling, it still needs further analysis in order to explain what caused the pteranodon to make such a drastic change. So even compelling theories are not immune to analysis. III is correct.