Nancy is aware that she is dreaming when she has a nightmare, so she concentrates and changes her dream from bad to good. this is a good example of dreaming.

Lucid

Explanation:

Here, the given example is of lucid dream because Nancy already new that she was dreaming. Another characteristic of a lucid dream is that the dreamer has a certain degree of control or can gain some control over what they are dreaming like the environment, the mood or the narrative. Here, Nancy also changed her dream from bad to good by concentrating and therefore, this is clearly an example of lucid dreaming.

i believe your answer is mountains.

permafrost layer, it exists beneath a layer of soil, rock or sediment.