This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Which of the following ultrasound marker is associated with greatest increased risk for Trisomy 21 in fetus? 
Select and explain. 
A. Echogenic foci in hea, B. Hyperechogenic bowel, C. Choroid plexus cysts, D. Nuchal edema
D: Nuchal edema
Answer: D: Nuchal edema 
Explanation: Ans. Nuchal edema