The conformer \( \text{CH}_2\text{OH}\text{CH}_2\text{OH} \) is the most stable form because it allows for favorable hydrogen bonding between the hydroxyl groups, enhancing stability.
Step 2: Conclusion.
The most stable conformer for ethylene glycol is \( \text{CH}_2\text{OH}\text{CH}_2\text{OH} \), corresponding to option (d).