The given reaction is a Wolff-Kishner reduction, which is used to reduce carbonyl groups (aldehydes and ketones) to alkanes.
The first step involves the formation of a hydrazone derivative: \[ \text{CH}_3 - \text{CO} - \text{CH}_2 - \text{CH}_3 \xrightarrow{\text{N}_2\text{H}_4} \text{CH}_3 - \text{C}(\text{NHNH}_2) - \text{CH}_2 - \text{CH}_3. \]
In the presence of ethylene glycol and KOH, the hydrazone undergoes decomposition to form: \[ \text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_3. \]
Thus, the product 'A' is butane.