Ais made up of all the living and nonliving factors in an area.
a. asteroid
b. ecosystem
c. continent

An Ecosystem is made up of all the living and nonliving factors in an area.

Why not an Asteroid nor a continent?

An asteroid is any small rocky object in the inner solar system.

A continent is one of several very large landmasses of the world. Such as North and South America, Australia, Africa, Europe and Asia.

Hope this helps you!