Which of the following mechanisms prevents self-pollination?

For a dioecious plant,which of the following is true?

Given below are two statements.
Statement $I$: Self-incompatibility is a device that prevents outbreeding.
Statement $II$: Self-incompatibility is a genetic mechanism due to which germination of pollen on the stigma of the same flower is inhibited.
In the light of the above two statements,choose the correct answer from the options given below.

Which of the following prevents pollen germination or pollen tube growth?

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

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