Which one of the given pollination technique/adaptation is...

Geitonogamy is a technique of self-pollination, in which pollen of one flower is deposited on the stigma of another flower of same plant. While others are mechanisms adopted by bisexual flowers to avoid self-pollination and promote cross-pollination. - Dichogamy The condition where maturing time of anther and stigma is different. Anther matures first, i.e. protandry, stigma matures first, i.e. protogyny. - Herkogamy Includes mechanical barrier in flower to ensure cross-pollination. - Heterostyle The height of stigma and anther is different to avoid self-pollination.