Arobin builds its nest on the branches of a maple tree, and the tree is not affected by the placement of the nest. this relationship is best described as

The correct answer is commensalism.

Explanation:

In biology, commensalism refers to an association among the individuals of two different species in which one species acquire food and other benefits from the other without benefiting or harming the other species.  

The species that get benefited due to the association is known as the commensal, who obtain shelter, nutrients, or support from the host species that is unaffected. The association is generally between the larger host and a smaller commensal. The given case is an illustration of commensalism. The host species remains unchanged, while the commensal one demonstrates great morphological changes.