What flower mechanism would help prevent pollination by a foreign plant species?

A) A pollen tube only grows inside the style of its own species.
B) The stigma is sticky mainly to its own species of pollen.
C) The timing of flowering keeps pollinators moving among a limited number of species.
D) Flowers attract a small number of specialized pollinators and, therefore, pollen is not spread equally to all available species of flowers.
E) All of the answer choices help prevent pollination by a foreign species.

All of the mechanisms listed would help prevent pollination by a foreign species. Option A would ensure that only compatible pollen from the same species can fertilize the ovules. Option B would reduce the chance of a foreign pollen grain successfully attaching to the stigma. Option C would limit the amount of time a pollinator spends on each flower, thus reducing the chance of it carrying foreign pollen to another species. Option D would limit the number of pollinators visiting a particular species of flower and reduce the chance of cross-pollination. Therefore, all of the options would help prevent pollination by a foreign plant species.