Which of the following definitions applies to permafrost?

a. a long, narrow, deep inlet of the sea between steep slopes.

b. permanently frozen subsoil, occurring in perennially frigid areas.

c. a treeless area between the icecap and the tree line of arctic regions, having permanently frozen subsoil and supporting low-growing vegetation such as lichens, mosses, and stunted shrubs.

d. a subarctic, evergreen coniferous forest of northern eurasia located just south of the tundra and dominated by firs and spruces