The monomer of the polymer

• Correct answer
  A

  
  
• B

  $\mathrm{CH}_3 \mathrm{CH}=\mathrm{CHCH}_3$
• C

  $\mathrm{CH}_3 \mathrm{CH}=\mathrm{CH}_2$
• D

  $\left(\mathrm{CH}_3\right)_2 \mathrm{C}=\mathrm{C}\left(\mathrm{CH}_3\right)_2$

Solution

The repeating unit in the given polymer is 2-methyl propene.
Related Theory The given polymer is an example of cationic polymerisation.

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