Final answer:
The abdominal cavity is the cavity below the chest that contains the digestive organs, which is part of the larger abdominopelvic cavity.
Step-by-step explanation:
The cavity below the chest that contains the digestive organs is known as the abdominal cavity. It is part of the abdominopelvic cavity, which fills the lower half of the trunk and also includes the pelvic cavity, housing the reproductive organs and organs of excretion.
The thoracic cavity, which is separate from the abdominopelvic cavity by the diaphragm, is above it and contains the lungs and the heart. Therefore, the correct answer to the student's question is b) Abdominal cavity.