All of the following interactions with the physical environment play a role in aiding plant reproduction, except:
a. seeds are carried by the wind and scattered across a landscape.
b. a bristles on some seeds attach to the hides of animals and are carried to new places.
c. the polien of flowers attaches to the legs of insects and is carried to other flowers.
d. guard cells open the stoma of plants, allowing air to enter a plant's leaf.