${\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{CH=C}}{{\text{H}}_2} + {\text{HBr}} \to$ A

A:

A: ${\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{CH(C}}{{\text{H}}_3}{\text{)Br}}$;

Most candidates gave the correct structure in (a).