Q. With reference to permafrost, consider the following statements:
1. Permafrost is any ground that remains completely frozen for at least two years straight.
2. The active layer of the permafrost stays frozen all year long.
3. Lower permafrost layers contain soils made mostly of minerals.
Which of the statements given above is/are correct?

[A] 1 and 2 only

[B] 2 and 3 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: C
Notes:
  • Statement 1 is correct: Permafrost is any ground that remains completely frozen—32 °F (0 °C) or colder—for at least two years straight. 
  • Statement 2 is incorrect: A layer of soil on top of permafrost does not stay frozen all year. This layer is called the active layer. This layer thaws during the warm summer months and freezes again in the fall. In colder regions, the ground rarely thaws—even in the summer. 
  • Statement 3 is correct: Near the surface, permafrost soils also contain large quantities of organic carbon—a material leftover from dead plants—that couldn’t decompose, or rot away, due to the cold. Lower permafrost layers contain soils made mostly of minerals. 

Source: Article