The number of trophic levels in the grazing food chain are restricted because of the:

Transmission of only 10% energy to successive levels

The correct answer is Option (2) → Transmission of only 10% energy to successive levels

The number of trophic levels in the grazing food chain is primarily restricted due to the transmission of only 10% energy to successive levels

The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level from the lower trophic level, with the remaining energy lost as heat, metabolic processes, and other factors. This significant energy loss limits the number of trophic levels, as there is eventually not enough energy to support additional levels.

So, the correct answer is: Transmission of only 10% energy to successive levels