$(i) \, (CH_3)_2CH-CH_2Br \xrightarrow{C_2H_5OH} (CH_3)_2CH-CH_2OC_2H_5 + HBr$
$(ii) \, (CH_3)_2CH-CH_2Br \xrightarrow{C_2H_5O^-} (CH_3)_2CH-CH_2OC_2H_5 + Br^-$
The reaction mechanisms for $(i)$ and $(ii)$ are respectively:

• A
  $S_{N^2}$ and $S_{N^2}$
• B
  $S_{N^2}$ and $S_{N^1}$
• C
  $S_{N^1}$ and $S_{N^2}$
• D
  $S_{N^1}$ and $S_{N^1}$