Which of the following best describes the impact of glaciers upon the surface of the earth? a. ice buried continents under a few hundred feet of ice. b. glaciers scraped across the surface and altered landscapes and the course of rivers. c. the passage of glaciers created new ecosystems. d. all of the above.

I find the best answer to be the following one:

B. Glaciers scraped across the surface and altered landscapes and the course of rivers.

The altered landscape can be described as: rather smooth landscape with characteristic rocks scattered though it.
The course of rivers is shaped because the rivers flow in the valleys through which the glaciers traveled.

While glacier-created landscape might support specific ecosystems, glaciers themselves did not create ecosystems, so I would keep to answer B.

In my opinion, the correct answer among the choices presented above is option B. Glaciers would impact the surface of the Earth by scraping  across the surface and altering landscapes and the course of rivers. Also, glaciers has the possibility to raise sea levels.