The correct answer is option 2: Lead.

Sindhoor or Kumkum is a red powder that is commonly used in Hindu religious ceremonies and is considered sacred. It is typically applied to the forehead, as a mark or symbol of auspiciousness.

The metal compound in Sindhoor or Kumkum is based on lead. Lead compounds are commonly used as pigments, due to their bright red color. Lead oxide, also known as red lead, is one such compound that is used in the production of Sindhoor or Kumkum.

It is important to note that lead is a toxic substance and prolonged exposure to it can have harmful effects on health, particularly in high doses. Therefore, it is advisable to use Sindhoor or Kumkum sparingly and avoid ingesting it or allowing it to come into contact with mucous membranes.

It is also worth mentioning that the usage of Sindhoor or Kumkum may vary across different regions or cultures, and alternative ingredients or compounds may be used in some cases.