This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gynae & OBS, Subject name: Medicine
Which of the following tests are helpful in diagnosing neural tube defect? 
Select and explain. 
A. Acetyl choline esterase in the amniotic fluid, B. Alpha-ketoglutarate in the amniotic fluid, C. Glutamate in the amniotic fluid, D. Beta hydroxyl butyrate in the amniotic fluid
A: Acetyl choline esterase in the amniotic fluid
Answer: A: Acetyl choline esterase in the amniotic fluid 
Explanation: Ans. (a) Acetyl choline esterase in the amniotic fluidRef.: Nelson 18th ed. / ch. 592* Failure of closure of the neural tube allows excretion of fetal substances (I+- - fetoprotein , acetylcholinesterase) into the amniotic fluid, serving as biochemical markers for a neural tube defect. Prenatal screening of maternal serum for AFP in the 16th to 18th wk of gestation is an effective method for identifying pregnancies at risk for fetuses with neural tube defects in utero.