One characteristic feature of tundra is that only the surface thaws in the summer and refreezes in the winter, leaving a layer of permanently frozen subsoil. This characteristic is known as

The appropriate answer is "Permafrost ".

Explanation:

Permafrost seems to be similar to other types of soil as well as the rock that has been managed to hold together with some ice.

The soil should therefore stay sealed well below 0 degrees Celsius for a minimum of 2 financial years to ever be taken into consideration permafrost. That very many permafrost would be observed in significant latitudes, just next to the northern and southern hemispheres, and that it could be found throughout lower elevations in mountainous areas.

The third one would be the answer