Which topic would an astronomer most likely study? the effect of water pollution on a local river
structures that can withstand earthquake damage
a movement of a population of dolphins
the formation and evolution of stars and galaxies

the formation and evolution of stars and galaxies

Explanation:

One of the topic an astronomer will most likely study is the formation and evolution of stars and galaxies.

Astronomers are scientists that studies the universe, its components and how it works.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.