Why do you suppose many different structures are needed by the digestive system

Mary has spontaneously decide to make a meal for friends. she is beginning to prepare fin fish and realizes she wants to also prepare a hearty dish ready to serve at the same time. what should she prepare? a: rice which take 20 minutes b: past which takes 15 minutesc: baked potatoes, which take 50 minutes.d: grilled garlic bread,which takes 5 minutes.e: boiled dumplings,which takes 17 minutes.