271. What is the amount of time required by erupting premolar to move through 1 mm of bone as measured on a bite – wing radigraph ?
A. 3-4 months
B. 4-5 months
C. 5-6 months
D. 6-7 months

272. Eruption date of decidous maxillary 2nd molar is ______________?
A. 20 months
B. 18 months
C. 24 months
D. 28 months