Answer: a. Interspecific competition
Step-by-step explanation:
The hummingbird drink the nectar from the flowers and robins eat plant seeds is the example of reduction of interspecific competition. The ecological niche of both of the species is different. An ecological niche can be define as the functional role an organism plays in an ecosystem.
In an interspecific competition, the individuals of distinct species compete for the same resource. This will lead to the extinction of any one of the species or decline in the members of the either of the species.
As the species of hummingbird is dependent upon the nectar and the robins are dependent upon the seeds as food therefore their will not be any interspecific competition among these species.