The correct options are
A CO2
B H2CO3
C CaC2
The following compounds are also used in inorganic chemistry.
1) Carbon Dioxide is used in many process like in extraction of elements it is used as reducing agent.
2)H2CO3 is called carbonic acid, which is a weak acid but studied in the theory of acids.
3)CaC2 is called calcium carbide, which is a source of calcium and also used in industry for the formation of other products like cacium cyanamide.
While (COOH)2 is purely an organic compound called oxalic acid. It is classified as dicarboxylic acid.
Hence option A, B and D is correct.