Generally the food chain has how many trophic levels

Name any two organisms which can occupy more than one trophic level in an ecosystem.

$A$ : Detritus food chain begins with detritus.

$R$ : Detrivores like fungi and bacteria are major decomposers in such food chains.

Transfer of energy from one trophic level to other trophic level is according to the second law of thermodynamics. The efficiency of energy transfer from herbivorous to carnivorous is

The second order consumer in a food chain is