Select the correct option for self-pollination in plants from the following.

Which one of the following characteristics promotes cross-pollination?

When the pollen grains are not transferred from anthers to the stigma in a flower due to a physical barrier or fence,or when some natural barrier exists between the androecium and gynoecium to check self-pollination,it is known as:

Continued self-pollination results in

List three strategies that a bisexual chasmogamous flower can evolve to prevent self-pollination (autogamy).

Which one of the following usually does $NOT$ promote self-pollination?