Answer: The answer is D: Trees that form an ecological island
Trees that form an ecological island is the phrase that describes a hammock.
Explanation: Hammock refers to a bed made of canvas with cords attached or fixed to support it at each end. Hammock is used for resting, sleeping and swinging. It is made up of a woven network of twine stretched with ropes between two firm points like posts or trees. Hammocks were for sleeping.