The correct answer is option D) phytoplankton and bacteria.
It is because of the fact that with advancement in trophic levels in a food chain or food web, energy is lost by 10%. So, the organism which is at lowest position in a food chain will have the most energy while the one at the top will have the least energy. It means that a primary consumer who feeds on plants will have 10% less energy than plants & a secondary consumer who feeds on a primary consumer will have 10% less energy than the primary one. Plants are at the base position in a food chain and phytoplanktons are microscopic algae which are considered as plants. So phytoplanktons will lie at the base position in a trophic level and they will have most available energy. So the correct answer is option D.