Air thermals are updrafts of warm air that rise from the ground into the sky. By flying in a spiral pattern
birds are able to ride these air currents to higher
altitudes.

What process enables birds to fly to higher altitudes without flapping their wings,
while riding these air thermals?

A. convection because warm air sinks and cool air rises.

B. convection because warm air rises and cool air sinks.

C. conduction because warm air sinks and cool air rises.

D. conduction because warm air rises and cool air sinks