$\mathrm{HBr}$ reacts with $\mathrm{CH}_2=\mathrm{CH}-\mathrm{OCH}_3$ under anhydrous conditions at room temperature to give

• A

  $\mathrm{CH}_3 \mathrm{CHO}$ and $\mathrm{CH}_3 \mathrm{Br}$
• B

  $\mathrm{BrCH}_2 \mathrm{CHO}$ and $\mathrm{CH}_3 \mathrm{OH}$
• C

  $\mathrm{BrCH}_2-\mathrm{CH}_2-\mathrm{OCH}_3$
• Correct answer
  D

  $\mathrm{H}_3 \mathrm{C}-\mathrm{CHBr}-\mathrm{OCH}_3$

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