Are made up of frozen volatile materials.
a. comets
b. asteroids
c. meteorites
d. meteroids

Which statement best describes a keystone species? o a. it has littlelmenetic variation. it has an extremely high population. 0 b. 0 c. it remains unaffected by all environmental changes. od. it has a strong influence on the ecosystem. 0 e. it's the first species to populate a new ecosystem.

In what for do plants utilize nitrogen? why do they need nitrogen?

Which of these is not a nucleotide base found in dna?