A peacock eats snakes which eat frogs. These eat hoppers which in turn thrive on leaves of the plants. The peacock is 

A food chain can be defined as a connection of various animals on the basis of their eating habits. Food chains consist of different trophic levels, and they also denote the flow of energy throughout the environment via organisms. 

In this question the leavers of the plant are the producers because they produce their own food and are not dependent on other organisms to fulfill their nutritional requirements. Grasshoppers are the primary consumers since they eat the producers. Frogs are the secondary consumers because they eat the primary consumers. Lastly, the organism that consumes the secondary consumer and is not being eaten by any other organism is present at the end or the apex of the food chain. In this case the peacock is the apex of the food chain. 

Hence the correct option would be D.