Self incompatibility is seen in

Self-incompatibility is a genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

Apple, tobacco, and potato are classic examples of plants that exhibit self-incompatibility.

Calotropis exhibits herkogamy (a physical barrier between the stigma and anther).

Sunflower exhibits dichogamy (specifically protandry, where anthers mature before the stigma).

Answer: Apple