Answer:
Directional selection
Explanation:
Directional selection is a type of natural selection that favors one extreme phenotype of a genetic trait due to its survival and reproductive advantage to the individuals over another extreme phenotype and the intermediate phenotype.
In the given example, the thick-leaved plants are better adapted to a drier climate due to reduced water loss. Directional selection favored the plants with thick leaves which in turn produced more progeny. Over the generations, the population evolved into the one having more number of thick-leaved plants.
D. Cannot repopulate the world with endangered organism
