During full annealing of steel, the component needs to be held above lower or higher critical temperature for _____ per cm of the thickness.

During full annealing of steel, the component needs to be held above l

1.	During full annealing of steel, the component needs to be held above lower or higher critical temperature for _____ per cm of the thickness.
A.	5 min
B.	13 min
C.	20 min
D.	25 min
Answer» D. 25 min