Which of the following statements about Down Syndrome patients is correct? A. Down syndrome patients have a decreased likelihood of developing Alzheimer disease. B. It is the most common cause of...

Which of the following statements about Down Syndrome patients is correct?

A. Down syndrome patients have a decreased likelihood of developing Alzheimer disease.

B. It is the most common cause of mental retardation.

C. It is always caused by three copies of chromosome 21, 2 paternal copies, and 1 maternal copy.

D. Infants are at increased risk for cardiac and intestinal manifestations, but have no increased risk of malignancy