Structural isomers share the same molecular formula but differ in atom connectivity.

Steps:

• Identify the molecular formula of compound Q from its skeletal formula (e.g., C₆H₁₄ for a hexane isomer).
• Calculate the molecular formula for each option's skeletal structure by counting carbons and inferring hydrogens.
• Compare formulas: matching ones are potential isomers; verify connectivity differs from Q.
• Select the option with identical formula to Q but rearranged carbon chain.

Why C is correct:

• C has the same C₆H₁₄ formula as Q but a branched chain, altering atom connections per isomer definition.

Why the others are wrong:

• A: Different formula (e.g., C₇H₁₆), adding an extra carbon.
• B: Identical structure to Q, not an isomer.
• D: Unsaturated bonds (e.g., C₆H₁₂), changing hydrogen count.

Final answer: C