Vitamin C,shown Below,is an Antioxidant That Undergoes Hydrogen Atom Abstraction

Vitamin C,shown below,is an antioxidant that undergoes hydrogen atom abstraction reaction with damaging radicals.Indicate which of the labeled hydrogens is prone to abstraction by a radical?

A) I
B) II
C) III
D) IV
E) All of the above can be abstracted with equal probability.