Which of the following compound is a gem-dihalide?

The correct answer is Option (3) → Methylene chloride

A gem-dihalide (geminal dihalide) is a compound in which two halogen atoms are attached to the same carbon atom.

Given compounds:

1. 1,2-Dichloroethane (Cl–CH₂–CH₂–Cl) → halogens on different carbons → not geminal
2. Ethylene dichloride → another name for 1,2-dichloroethane → same as above
3. Methylene chloride (CH₂Cl₂) → both Cl atoms on same carbon → gem-dihalide 
4. Benzyl chloride (C₆H₅–CH₂Cl) → only one Cl atom → not geminal