Final answer:
The 'islands of life' deep within the desert are known as oases, which are vital to the survival of people living in arid regions by providing water and habitable land.
Step-by-step explanation:
These "islands of life" deep within the desert where erosion has lowered the land surface are c. Oases. Oases are green areas formed around underground water sources that reach the surface, creating an environment where plant and animal life can exist, and where human activities, such as farming and herding, can take place on a restricted basis.
Although they make up just a tiny fraction of the desert's landmass, oases are vital to the survival of people living in these arid regions, providing them with water and a place to settle.