Answer:
Decomposition Reaction.
Definitions
---> Hydrogen is a colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. Symbol: H; atomic weight: 1.00797; atomic number: 1; density: 0.0899 g/1 at 0°C and 760mm pressure.
---> Oxygen is a colorless, odorless, gaseous element constituting about one-fifth of the volume of the atmosphere and present in a combined state in nature. It is the supporter of combustion in air and was the standard of atomic, combining, and molecular weights until 1961, when carbon 12 became the new standard. Symbol: O; atomic weight: 15.9994; atomic number: 8; density: 1.4290 g/1 at 0°C and 760mm pressure.
---> Sulfur is a nonmetallic element that exists in several forms, the ordinary one being a yellow rhombic crystalline solid, and that burns with a blue flame and a suffocating odor: used especially in making gunpowder and matches, in medicine, in vulcanizing rubber, etc. Symbol: S; atomic weight: 32.064; atomic number: 16; specific gravity: 2.07 at 20°C.
---> Carbon is a widely distributed element that forms organic compounds in combination with hydrogen, oxygen, etc., and that occurs in a pure state as diamond and graphite, and in an impure state as charcoal. Symbol: C; atomic weight: 12.011; atomic number: 6; specific gravity: (of diamond) 3.51 at 20°C; (of graphite) 2.26 at 20°C.
--> Decomposition is the act or process of decomposing, separating or resolving into constituent parts or elements.
---> Synthesis is the combining of the constituent elements of separate material or abstract entities into a single or unified entity (opposed to analysis,) the separating of any material or abstract entity into its constituent elements.
In a decomposition reaction, a single compound breaks down into two or more simpler substances. In this case, the compound H2SO3 is decomposed into the simpler substances H2O and SO2. Therefore, the correct answer is (b) Decomposition.