Down Syndrome

Which of the following is the Karyotyping for Down syndrome?

Which of the following is the commonest cause of Down syndrome?

Which of the following is the commonest cause of congenital heart defect in newborn with Down syndrome?

Which of the following were clinical features of Down syndrome?

A day 3 of life term newborn girl was suspected to be having trisomy 21 in view of dysmorphic features. The mother raised the concern of her baby has not passing motion since birth and developed abdominal distension. Per abdominal examination noted distended abdomen with gushing of air on per rectal. What is the possible diagnosis of this baby?