The correct option is B Etaerio of berries
A custard apple fruit develops from a polycarpellary and apocarpous ovary. It forms from the pistils and receptacle of one flower. Custard apple is an aggregate fruit but the components of aggregate fruit are difficult to define. In custard apple, fruit are made up of individual berry-like pistils fused with the receptacle while other aggregate fruits can develop from the merger of several ovaries that were separate in a single flower.
Not all flowers with multiple ovaries form aggregate fruit; the ovaries of some flowers do not become tightly joined together to make a larger fruit.
Thus, custard apple is an etaerio of berries.
Therefore, the correct answer is option B.