To solve this problem, we need to understand the energy transfer through the food chain:$\newline$Plant → Mice → Snake → Peacock.$\newline$In ecological food chains, energy transfer between trophic levels is typically about 10\% efficient.$\newline$Let's calculate the energy available to each level:$\newline \bullet$Energy at the producer level (Plant) is 20 J.$\newline \bullet$Energy transferred to the primary consumer (Mice) is 10\% of 20 J:$\newline$ - Energy for Mice = 0.1 \times 20 = 2 J.$\newline \bullet$Energy transferred to the secondary consumer (Snake) is 10\% of 2 J:$\newline$ - Energy for Snake = 0.1 \times 2 = 0.2 J.$\newline \bullet$Energy transferred to the tertiary consumer (Peacock) is 10\% of 0.2 J:$\newline$ - Energy for Peacock = 0.1 \times 0.2 = 0.02 J.$\newline$Therefore, the energy available to the peacock as food is 0.02 J.$\newline$This corresponds to Option 1.