Identifying structural isomers by molecular formula and connectivity

Steps:

• Determine the molecular formula of compound Q from its skeletal structure.
• Calculate the molecular formula for each option's skeletal structure.
• Compare formulas: structural isomers must match Q's formula exactly.
• Check connectivity: isomers have different atom arrangements but same formula.

Why C is correct:

• Option C has the same molecular formula as Q but different carbon chain branching, fitting the definition of a structural isomer.

Why the others are wrong:

• A has a different molecular formula, so not an isomer.
• B matches the formula but identical connectivity to Q, making it the same compound.
• D has fewer carbon atoms, violating the isomer formula requirement.

Not enough information on exact structures of Q and options to verify fully.

Final answer: C