This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Embryology 2, Subject name: Anatomy
All are true about Somites except:- 
Select and explain. 
A. 4th week is called somite period, B. Dorsi-lateral pa forms the sclerotome, C. 44 pairs are present by the end of 1st month., D. Post otic pa of each paraxial mesoderm is subdivided into a number of cubical blocks known as somites.
B: Dorsi-lateral pa forms the sclerotome
Answer: B: Dorsi-lateral pa forms the sclerotome 
Explanation: The post otic pa of paraxial mesoderm form bilateral solid cord of cells extending along the side of notochord beneath the neural tube. It undergoes segmentation to form series of paired somites. The somites are differentiated into ventro medial (sclerotome)and dorso lateral pa (dermomyotome) The somites appear between 20-30 days of development and by the end of first month, 44 pairs of somites are laid down. Thus, the 4th week of development is known as somite period. Out of 44 pairs of post otic somites: 4 are occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 8-12 coccygeal.