What happens when ethylene glycol reacts with periodic acid? 

Formaldehyde is produced

The correct answer is option 1. Formaldehyde is produced.

When ethylene glycol reacts with periodic acid, the predicted product is formaldehyde.

Periodic acid \((HIO_4)\) is a strong oxidizing agent that can cleave vicinal diols (two hydroxyl groups on adjacent carbons) into carbonyl compounds (aldehydes or ketones). In the case of ethylene glycol, which is a vicinal diol, the carbon-carbon bond between the two hydroxyl groups is cleaved, forming two formaldehyde molecules.