A 4-month old infant is brought to the physician for a routine examination. Physical examination shows epicanthic folds and a palmar simian crease. Cytogenetic testing shows an autosomal trisomy. 
Which of the following cardiac anomalies is most commonly associated with this condition?
Atrial septal defect
Complete Atrioventricularseptal defect
Mitral stenosis
Patent ductusarteriosus