One bromine atom becomes attached to the first carbon in the first stage of the reaction. The 2nd carbon becomes positive and bond with a water molecule which then loses a proton to form a hydroxyl group.
H2C=CHCH2CH2CH3 + Br2 --> BrH2C-CH(+)CH2CH2CH3 + Br-
BrH2C-CH(+)CH2CH2CH3 + H2O --> BrH2C-CH(OH2+)CH2CH2CH3
BrH2C-CH(OH2+)CH2CH2CH3 --> BrH2CCH(OH)CH2CH2CH3 + H+
This should tell you which of the answers is my choice.