Step 1: Follow the carbon count:
Oxidative cleavage does not remove carbons from the ring. Cyclohexene has 6 carbons, so the product must have 6 carbons in one chain.
Step 2: Track the double bond:
Cutting the ring at the C=C opens it into a chain with two new ends. Each end carbon had one H and gets oxidised to $\text{COOH}$.
Step 3: Write the structure:
\[ \text{HOOC-CH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{-COOH} \]
This is hexanedioic acid, option C.
Final Answer:
Ring-opening oxidation gives adipic acid, hexane-1,6-dioic acid.
\[ \boxed{\text{(C) }\text{hexane-1,6-dioic acid}} \]