The blank can be correctly filled up with decreases.
The major portion energy is lost as it transfers from one trophic level to the next in a food chain.
It is because most of the energy present at any trophic level is used for various life processes such as movement, reproduction et cetera through cellular respiration.
It is ultimately lost as heat to the surroundings.
It is estimated that only 10% of the energy available at any trophic level is passed on to the next trophic level.
