The correct option is B Cleistogamy
Pollination occurring in closed flowers is cleistogamy. It is a condition in which flower does not open. It is an adaptation seen in plants to ensure self-pollination. In such flowers, the anthers and stigma lie close to each other. When anther dehisces in the flower buds, pollen grains come in contact with stigma to pollinate, e.g., Arachis hypogaea. It ensures seed formation even in the absences of any pollinating agent. It is cheaper for the plant as there is no costly nectar or fragrance which the plant has to produce for pollination. The disadvantage of cleistogamy is that the offsprings produced have limited genetic diversity.