Points of arrest for iron correspond to__________________?

(A) stages at which allotropic forms change ()
(B) stages at which properties do not change with increase in temperature (X)
(C)  stages at which further heating does not increase temperature for some time (X)
(D) there is nothing like points of arrest (X)
(E) none of the above (X)

Answers: Points of arrest for iron correspond to stages at which allotropic forms change.