Polyembryony is a phenomenon in which multiple embryos are formed from a single fertilized egg. Among the options given, the best example of polyembryony is citrus plants. In citrus plants, such as oranges and lemons, several embryos can develop from a single seed. This occurs due to the presence of multiple embryos within the ovule of a citrus flower. Each of these embryos has the potential to develop into a new plant.
Options 1, 2, and 4 are not the best examples of polyembryony. Cocoa, capsicum (bell peppers), and cycas (a type of palm tree) do not typically exhibit polyembryony. While some degree of polyembryony may occur in these plants, it is not as notable or common as in citrus plants.
Therefore, option 3, Citrus, is the best example of polyembryony out of the given options.