This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
Concerning contraction of the diaphragm: 
Select and explain. 
A. The nerves that are responsible emerge from the spinal cord at the level of the lower thorax, B. It tends to flatten the diaphragm, C. It reduces the lateral distance between the lower rib margins, D. It causes the anterior abdominal wall to move in
B: It tends to flatten the diaphragm
Answer: B: It tends to flatten the diaphragm 
Explanation: When the diaphragm contracts, it becomes flatter The phrenic nerves that innervate the diaphragm come from high in the neck, that is, cervical segments 3, 4, and 5. Contraction of the diaphragm causes the lateral distance between the lower rib margins to increase and anterior abdominal wall to move out. The intrapleural pressure is reduced because the larger volume of the chest cage increases the recoil pressure of the lung.