Choose the halogen which is most reactive towards \( \mathrm{S_{N}1} \) reaction in the given compounds (A, B, C and D)?
A – \( \mathrm{Br}_{(b)} \); B – \( \mathrm{I}_{(b)} \); C – \( \mathrm{Br}_{(b)}\); D – \( \mathrm{Br}_{(b)} \)
A – \( \mathrm{Br}_{(b)} \); B – \( \mathrm{I}_{(a)} \); C – \( \mathrm{Br}_{(a)} \); D – \( \mathrm{Br}_{(a)} \)
A – \( \mathrm{Br}_{(a)} \); B – \( \mathrm{I}_{(a)} \); C – \( \mathrm{Br}_{(a)} \); D – \( \mathrm{Br}_{(a)} \)
A – \( \mathrm{Br}_{(a)} \); B – \( \mathrm{I}_{(a)} \); C – \( \mathrm{Br}_{(b)} \); D – \( \mathrm{Br}_{(a)} \)