Look at the pic it is the question.
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Arrows :

It shows how energy and nutrients are transferred from plants (producers) to herbivores and carnivores and through to decomposers. ... The arrows in the food chain below depict the direction in which energy and nutrients flow, i.e. the arrow always points from the eaten to the eater.

Greatest amount of energy transferred: Grass aka Autotrophs.

A sequence of living organisms which involves the transfer of food energy from producers, through a series of organisms with repeated eating and being eaten is called food chain. Each level or step in a food chain where the transfer of energy takes place is called trophic level. According to the pyramid of energy, the energy content is maximum in autotrophs or producers. Autotrophs are the plants which prepare their food by photosynthesis. They are the primary producers and primary source of food energy. The flow of energy is unidirectional from producer to consumer level. The energy decreases at each trophic level of the food chain, as part of the energy is lost as heat and major part of the energy is liberated during respiration for use in various activities. Only 10% of the energy of previous trophic level is received by next trophic level, as proposed by 10 percent law of Lindeman.