The IUPAC name of $\mathrm{(CH_3)_2CH{-}CH_2Br}$ is

1. Identify the longest CARBON chain containing the halogen-bearing carbon. 2. Structure: $\mathrm{(CH_3)_2CH{-}CH_2{-}Br}$ → 3 carbons in the chain ($\mathrm{CH_3{-}CH(CH_3){-}CH_2{-}Br}$, with a methyl branch). 3. Number from the end closest to the halogen: C1 = CH$_2$Br, C2 = CH, C3 = CH$_3$. C2 has a methyl substituent. 4. Parent: propane. Halogen at C1: 'bromo'. Branch at C2: 'methyl'. Substitutents in alphabetical order: 1-BROMO-2-METHYLPROPANE. 5. Option A would correspond to $\mathrm{CH_3CH_2CH_2CH_2Br}$ (straight 4-C chain). Option B is $\mathrm{(CH_3)_3CBr}$ (tert-butyl). Option D is $\mathrm{CH_3CHBr CH_2CH_3}$ (Br on C2 of butane). _Source: syllabus Chemistry Part 2, Ch 6, §6.2 (Nomenclature — IUPAC rules), p. 2–3._