This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology, Subject name: Anatomy
T cell migration occurs to tonsil occurs at intrauterine age of: 
Select and explain. 
A. 6 - 7 weeks, B. 10 - 11 weeks, C. 14 - 15 weeks, D. 18 - 19 weeks
D: 18 - 19 weeks
Answer: D: 18 - 19 weeks 
Explanation: Ans: d (18-19 wks)Ref: Human Embryology by I B Singh, 8th edi., Pg. 147\IU ageDevelopmental events4 weeks2 lateral lingual swellings & tuberculum impar5 weeksHypobranchial eminence6 weeksDental lamina of upper & lower jaw7 weeksSalivary glands8 weeksEnamel organs3 monthsFormation of tonsil5 monthsTonsil infiltrated by lymphatic tissue6 monthsTongue formation complete