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
Earliest detectable Congenital Malformation by USG is: 
Select and explain. 
A. Spina bifida, B. Cystic hygroma, C. Anencephaly, D. Encephalocele
C: Anencephaly
Answer: C: Anencephaly 
Explanation: Anencephaly