Why do weather fronts happen

In a scientific experiment, a is any factor that can be changed or be changed

The covers all of earth like a thin shell,but it is not a solid sheet of material.it is broken up into several large sections and many smaller ones. fill in the blank.

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.