Spina Bifida Is One of the Most Prevalent of Human

Multiple Choice

Spina bifida is one of the most prevalent of human birth defects.The defect usually involves the spinal cord or the spinal canal opening to the outside of the body.In severe cases,movement of the legs may be limited or entirely absent.At which stage of development is this defect likely to occur?

A) formation of the neural tube
B) formation of the gastrula
C) formation of the notochord
D) formation of the somites
E) formation of the lateral mesoderm