When an isomer Y with molecular formula $\text{C}_4\text{H}_9\text{Br}$ is hydrolysed in aqueous alkali to give an alcohol $\text{C}_4\text{H}_9\text{OH}$, the reaction rate is observed to remain unchanged when the concentration of $\text{OH}^-$ ions present is altered. Which molecular structure of Y is the most likely?
- A$ ext{CH}_3 ext{CH}_2 ext{CH}_2 ext{CH}_2 ext{Br}$
- B$ ext{CH}_3 ext{CH}_2 ext{CHBr} ext{CH}_3$
- C$( ext{CH}_3 )_2 ext{CHCH}_2 ext{Br}$
- D$( ext{CH}_3 )_3 ext{CBr}$