The author views the idea that the pterosaurs became airborne by rising into light winds created by waves as:
Unlikely
The author mentions in the last line of the passage that the idea that the pterosaurs became airborne by rising into light winds created by waves calls for high waves to channel updrafts. The wind that made such waves however, might have been too strong for the pterosaurs to control their flight once airborne. Thus this idea is viewed by the author as “unlikely” making answer option (b) the correct answer choice.