Step 1: Identify ethylene glycol.
Ethylene glycol is a dihydric alcohol:
\[
HO-CH_2-CH_2-OH
\]
Step 2: Strong oxidation converts glycol to dicarboxylic acid.
Under strong oxidizing conditions, both terminal \(-CH_2OH\) groups are oxidized to \(-COOH\).
Step 3: Oxidant required for complete oxidation.
Alkaline KMnO\(_4\) is a strong oxidizing agent that oxidizes ethylene glycol to oxalic acid:
\[
HOCH_2CH_2OH \xrightarrow{alk. KMnO_4} HOOC-COOH
\]
Step 4: Conclusion.
Thus alkaline KMnO\(_4\) gives oxalic acid.
Final Answer:
\[
\boxed{\text{(C) alkaline KMnO\(_4\)}}
\]