Correct option (c) less than 50%
The source of energy in all ecosystem is solar energy. About 50% of the solar energy incident over earth rs present in PAR (Photosynthetically active Radiation). About 1-5% of incident solar radiation or 2-10%, of PAR is captured by the photosynthetic organisms in the synthesis of organic matter (gross primary productivity). Roughll. 20% of it is consumed in respiration so that net capture of energy (net primary productivity) is 0.8-4% of incident radiation or 1.6-8% of PAR.