In a nucleophilic substitution reaction : $\text{R}-\text{Br}+{\text{Cl}}^{-}\stackrel{\text{DMF}}{⟶}\text{R}-\text{Cl}+{\text{Br}}^{-}$ ,  which one of the following undergoes complete inversion of configuration ?

• A

  C₆H₅CHC₆H₅Br
• B

  C₆H₅CCH₃C₆H₅Br
• C

  C₆H₅CH₂Br
• Correct answer
  D

  C₆H₅CH₂CH₂Br

Hence, the correct answer is option: 'D'.