Prickly pear cactus plants are well adapted to desert conditions. The stems are the flattened structures visible in the image and the leaves are reduced to spines. The white spots in the image are groups of spines.

Prickly pear cactus plants are well adapted to desert conditions. The stems are the flattened structures visible in the image and the leaves are reduced to spines. The white spots in the image are groups of spines.

[Source: Stan Shebs/Wikimedia. File licensed under CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)]

Which characteristic describes the advantage of one of their adaptations?