Which biome contains permafrost?
a. tundra
b. taiga
c. temperate rain forest
d. temperate deciduous forest

It is tundra biome which has permafrost. So, option A. is correct.

Permafrost means frozen soil, rock or sediment for at least two consecutive years. Permafrost is characteristic feature of Tundra biome. The tundra biome gets slanting sun rays throughout the year because they lie at poles. In contrast to slanting sun rays, direct sun rays cause more heat. Since the sun rays are not direct in Tundra that is why temperature in Tundra biomes is extremely low. This lower temperature throughout the year leads to permafrost soil.