This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CVS Embryology, Subject name: Anatomy
[{'content': 'Closure of the foramen primum results from fusion of which of the following structures? \nSelect and explain. \nA. Septum secundum and the fused atrioventricular cushions, B. Septum secundum and the septum primum, C. Septum primum and the fused atrioventricular cushions, D. Septum primum and the septum spurium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C. The foramen primum forms between the free edge of the septum primum and the atrioventricular (AV) cushions. It is closed when the septum primum fuses with the AV cushions.', 'role': 'assistant'}]