Option 1 suggests that only Benzene is used as a dry cleaning chemical. Benzene was used in the past; however, due to safety concerns, it is no longer used widely for this purpose.

Option 2 suggests that only Carbon Tetrachloride is used. This was once common, but its use has declined due to health risks and environmental concerns.

Option 3, the correct answer, indicates that Benzene, Carbon Tetrachloride, and Trichloroethylene are used as dry cleaning chemicals. While Benzene and Carbon Tetrachloride are not as commonly used today due to safety and environmental issues, Trichloroethylene is still used and is considered a standard solvent for dry cleaning.

Option 4 suggests that all four chemicals, including Sodium Carbonate, are used. This is incorrect because Sodium Carbonate is not a dry cleaning chemical. It is a type of salt used in various industrial processes, but not typically for dry cleaning.