Which of the Following Is the Most Reactive Substrate in an E2

Multiple Choice

Which of the following is the most reactive substrate in an E2 reaction? $\mathrm { CH } _ { 3 } \mathrm { Br } \quad \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { Br } \quad \mathrm { CH } _ { 3 } \mathrm { CH } \left( \mathrm { Br } ^ { 2 } \right) \mathrm { CH } _ { 2 } \mathrm { CH } _ { 3 } \quad \left( \mathrm { CH } _ { 3 } \right) _ { 3 } \mathrm { CBr }$
I $\quad\quad\quad\quad\quad\quad\quad$ II $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad$ III $\quad\quad\quad\quad\quad\quad\quad\quad$ IV

A) I
B) II
C) III
D) IV