Answer:
Cactus's have many adaptions to survive in dry, hot regions. Such as:
- Being greyish/silver in color: To reflect heat of the sun and reduce water loss
- A swollen stem: To store water
- Rolled up leaves (only in certain cactus's) to reduce surface area that is exposed to the sun, therefore preventing water loss
- Covered in thorns: Helps protect the plant from animals trying to eat it
Hope that helps!