What is the function of the filiform apparatus during the entry of the pollen tube into the ovule?

• A
  It triggers the opening of the pollen tube.
• B
  It guides the pollen tube from the synergids towards the egg cell.
• C
  It helps in the entry of the pollen tube into the synergids.
• D
  It prevents the entry of more than one pollen tube into the embryo sac.