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

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