Answer:
Adaptation must fit the environment.
Step-by-step explanation:
Adaptations are the behavioral, structural or functional modifications exhibited by living beings to make themselves better fitted in their respective habitat. Since different habitats have different environmental conditions, certain trait can serve as adaptations in one environment but not another.
Example: Reduction of leaves into spines is adaptive feature in dry environment to reduce the water loss. But it is not desirable in tropical environmental conditions where ample of water is available.