A gardener crosses a rose plant with the fewest number of thorns with another rose plant with fewer thorns. a. gene modification
b. artificial selection

A

Explanation:

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.