Protandry is a problem in:

✅Explanation:
-Protandry is a condition in which the male reproductive organs (anthers) of a flower mature and release pollen before the female reproductive organs (stigma) are receptive. This can lead to difficulties in pollination and fertilization, resulting in reduced fruit set.
Protandry is a significant issue in walnut cultivation as it can hinder natural pollination and necessitate hand-pollination or the planting of pollinator varieties to ensure adequate fruit set.

🛑Other Options Explanations:
-Option A: Banana: Bananas are predominantly parthenocarpic, meaning they develop fruit without fertilization.
-Option C: Papaya: Papaya has separate male and female plants.