The correct answer is option 1, which is "Sulphur based."

Sulphur-based chemicals are commonly used in beauty parlours for hair-setting. These chemicals help in the process of perming or curling the hair. They work by breaking the disulfide bonds in the hair and reshaping them into the desired style. One commonly used sulphur-based chemical for hair-setting is ammonium thioglycolate.

Option 2, "Phosphorus based," is not correct. Phosphorus is not typically used in beauty parlours for hair-setting purposes.

Option 3, "Silicon based," is also not correct. Although silicon-based products are used in hair care, such as shampoos or conditioners, they are not typically used for hair-setting.

Option 4, "Iron based," is not correct either. Iron is not used in beauty parlours for hair-setting. Iron is more commonly associated with straightening the hair using a flat iron or curling iron.

In summary, option 1 (Sulphur based) is the correct answer as sulphur-based chemicals are commonly used in beauty parlours for hair-setting.