Which of the following is used for removing grease and stains from woollen clothes? 

Ammonium hydroxide 

The correct answer is option 1. Ammonium hydroxide.

Ammonium hydroxide, often referred to as ammonia solution, is a chemical compound consisting of ammonia (NH₃) dissolved in water. It is a versatile cleaning agent and is commonly used in household cleaning products. When it comes to removing grease and stains from woolen clothes, ammonia solution has several properties that make it effective:

1. Alkaline Nature:  Ammonium hydroxide is alkaline, meaning it has a high pH. The alkalinity helps to break down and solubilize greasy and oily substances, making it effective in removing grease stains from woolen fabrics.

2. Solubility:  Ammonium hydroxide has good solubility in water, allowing it to mix well and spread over the stained area. This helps in lifting and dissolving the greasy or oily components of stains.

3. Gentle on Wool: Ammonium hydroxide is generally considered milder than some other alkaline cleaning agents. This is important when dealing with delicate fabrics like wool, as harsh chemicals could damage or discolor the material.

When using ammonium hydroxide for stain removal on woolen clothes, it is essential to follow recommended guidelines, use appropriate concentrations, and test a small, inconspicuous area first to ensure compatibility with the fabric.