$A$ - Cellulose is a heteropolymer.
$R$ - Cellulose is made up of only one type of amino acid.

• A
  $A$ and $R$ are correct.
• B
  $A$ and $R$ are incorrect.
• C
  $A$ is correct and $R$ is incorrect.
• D
  $A$ is incorrect and $R$ is correct.