Question

which of these statements about airplane and rocket flight is true?
a. only one must overcome the force of gravity.
b. only one requires air molecules to generate lift.
c. only one requires combustion reactions to generate thrust.
d. only one requires both fuel and an oxidizer for the combustion reaction.

Explanation:

Airplanes rely on air molecules flowing over their wings to create lift via Bernoulli's principle, so they cannot operate in the vacuum of space. Rockets generate thrust via combustion and do not depend on air for lift; they can travel through space. For the other options: both airplanes and rockets must overcome gravity; both use combustion for thrust; rockets carry both fuel and oxidizer, while airplanes use atmospheric oxygen, meaning option D is incorrect as the statement does not match this reality.

Answer:

B. Only one requires air molecules to generate lift.