Which of the following type of flowers produce assured seed-set even in the absence of pollinators?

Cleistogamous flowers do not open at all. In such flowers the anthers and stigma lie close to each other. When anthers dehisce in the flower buds pollen grains come in contact with the stigma to effect pollination. Therefore there is assured seed set even in the absence of pollinators.
Chasmogamous flowers have exposed anther and stigma. Therefore can be pollinated by pollinators.
Unisexual and dioecious flowers also need pollinators.