Which one of the following shows a unique relationship with an insect that has coevolved with it and that is the only insect that can pollinate this tree?

The correct option is Fig.

Let's understand the unique relationship between fig trees and their pollinators step-by-step:

1. Coevolution and Mutualism: Fig trees (species of the genus Ficus) and fig wasps (family Agaonidae) share a classic example of obligate mutualism. This means neither the tree nor the wasp can complete their life cycle without the other. They have coevolved over millions of years, resulting in a highly specialized, one-to-one relationship.


2. The Syconium: The "fruit" of a fig is actually an inverted inflorescence called a syconium. It is a hollow, fleshy structure lined on the inside with hundreds of tiny, male and female flowers. The only access to the inside of the syconium is a tiny pore at the end called an ostiole.


3. Specificity of Pollination: Because the ostiole is extremely small and the internal structure is unique, only the female wasp of a specific, coevolved fig wasp species can squeeze inside. When she enters the syconium to lay her eggs, she simultaneously deposits pollen from the fig tree she was born in, fertilizing the internal flowers.