Concering the development of the human heart, which of the following is correct?
A. The aorticopulmonary septum develops in part from the truncus arteriosus.
B. The coronary sinus develops from the right sinus horn.
C. The ostium secundum develops at birth.
D. The pulmonary trunk develops from the 4th aortic arch.
E. The smooth-walled portion of the left atrium is derived from the sinus venosus.