The correct answer is Option (1) → (A), (C) and (D) only
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(A) Net primary productivity is available to consumers: This is true. Net primary productivity (NPP) is the amount of energy available to the consumers after plants use some of it for their own growth and respiration. It represents the energy available to herbivores and higher trophic levels.
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(B) Secondary productivity increases with each trophic level: This is incorrect. Secondary productivity refers to the energy passed on to the next trophic level (usually through consumers). However, secondary productivity tends to decrease at each successive trophic level because of energy loss due to inefficient transfer (as per the 10% energy transfer rule).
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(C) The growth of the food chain is limited by the inefficiency of energy transfer: This is true. Energy transfer between trophic levels is inefficient, and typically only about 10% of the energy from one trophic level is passed on to the next, which limits the number of trophic levels in a food chain.
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(D) About 90% of energy at one trophic level does not appear at the next level: This is true. According to the 10% energy rule, about 90% of energy is lost in the form of heat, respiration, and waste at each trophic level, and only about 10% is passed to the next level.
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