Which of the following statements are correct ? (i) In an aquatic ecosystem, DFC is the major conduit for energy flow. (ii) In a terrestrial ecosystem, a much larger fraction of energy flows through the GFC than through the detritus food chain. (iii) In a natural ecosystem, some animals like cockroaches, crows, etc., are only carnivores. (iv) Each trophic level has a certain mass of living material at a particular time called as the standing state. (v) The standing crop is measured as the mass of living organisms or the number in a unit area. (vi) The biomass of a species is expressed in terms of fresh or dry weight. (vii) Measurement of biomass in terms of fresh weight is more accurate.