The correct option is B To guide the pollen tube into the synergids
The synergids have cellular thickenings called filiform apparatus at the micropylar end. The function of the filiform apparatus is to guide the pollen tube into the synergids. The pollen tube creates an opening in the embryo sac with the help of certain enzymes and not the filiform apparatus. Filiform apparatus has no role to play in seed formation either.