In the food chains given below. Select the most efficient food chain in terms of energy :

The most efficient food chain in terms of energy is Phytoplankton $\rightarrow$ Zooplankton $\rightarrow$ Small Fish $\rightarrow$ Big Fish. This is because phytoplankton are the primary producers and they convert the solar energy into chemical energy, which is then transferred to the next trophic level. This food chain has the least energy loss as it has the least number of trophic levels.