One example of how one sphere interacts with another

At a continent-continent convergence,

What body of water is the second cataract of the nile river submerged under

The vegetation that thrives in the tundra is limited to a. mosses, barley, wheat, and corn. b. coniferous trees. c. dwarf shrubs, mosses, lichen, potatoes, and beans. d. mosses, lichen, algae, and dwarf shrubs.