my answer would b A, as it serves the question more appropriately..
if u wish to say that all the reactions appear to be losing and gaining electrons,
then, your answer should not be acid-base reactions...it should instead be redox reactions....
if u noticed, the first reaction does not have an exchange of electrons,it only has a formation of an ionic bond....
reaction 2 is definitely a redox reaction, as I- loses its electrons to Ce4+....
the second reaction however, is unbalanced and to balance it, u add a 2 in front of Ce3+..
the third reaction is an acid-base reaction,as the NH3 gains a proton (H+), and the HOAc loses its proton.....
so, the answer should be A..
hope that helps..
mail me if u need more help..