Polymer repeat units indicate branch at carbon 2, matching 2-ene naming

Steps:

• Analyze repeat unit of J: -[CH2-CH(CH3)]-, branch (CH3) attached to carbon 2.
• Analyze repeat unit of K: -[CH2-CH(C6H5)]-, branch (C6H5) attached to carbon 2.
• In addition polymerization, branch position reflects substituted carbon adjacent to terminal in monomer.
• Match to alkene naming where double bond starts at position 2 for internal substitution pattern.

Why D is correct:

• D names both as 2-enes, aligning with definition of internal alkenes where substitution occurs at carbon 2 or 3, consistent with branch location in repeat units per IUPAC alkene nomenclature.

Why the others are wrong:

• A uses 1-enes, which imply terminal double bonds without carbon 2 branch specificity.
• B uses 1-enes, ignoring internal branch positioning in polymer structure.
• C uses mixed enes, failing to consistently match carbon 2 branch for both polymers.

Final answer: D