What Flower Mechanism Would Not Help Prevent Pollination by a Foreign

What flower mechanism would not 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) Flowers of different plant species bloom at the same time with flowers of similar shape,size,and color.