The author views the idea that the pterosaurs became airborne by rising into light winds created by waves as ______.

A．They were unable to fold their wings when not in use.
B．They hung upside down from branches as bats do before flight.
C．They flew in order to capture prey.
D．They were an early stage in the evolution of the birds.

A．New evidence is introduced to support a traditional point of view.
B．Three explanations for a phenomenon are presented, and each is disputed by means of specific information.
C．Three hypotheses are outlined, and evidence supporting each is given.
D．Recent discoveries are described, and their implications for future study are projected