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: Dental
The first sign of future deciduous teeth as a thickening of oral ectoderm appears at about 
Select and explain. 
A. 25th day of Intra uterine life, B. 34th day of Intra uterine life, C. 56th day of Intra uterine life, D. 20 wks of Intra uterine life
C: 56th day of Intra uterine life
Answer: C: 56th day of Intra uterine life 
Explanation: None