Choose the halogen which is most reactive towards SN1 reaction in the given compounds (A, B, C & D)
A.

B.

C.

D.

A

$$A - Br_{(b)}; B - I_{(a)}; C - Br_{(a)}; D - Br_{(a)}$$

B

$$A - Br_{(b)}; B - I_{(b)}; C - Br_{(b)}; D - Br_{(b)}$$

C

$$A - Br_{(a)}; B - I_{(a)}; C - Br_{(b)}; D - Br_{(a)}$$

D

$$A - Br_{(a)}; B - I_{(a)}; C - Br_{(a)}; D - Br_{(a)}$$