An organic compound 'A' `(C_2H_6O)` reacts with sodium to form a compound 'B' with the evolution of hydrogen gas and gives a yellow compound 'C' when treated with iodine and NaOH. When heated with conc. `H_2SO_4` at `140^@C` it gives a compound 'D' `C_4H_(10)` which on treatment with HI at `100^@C` gives 'E'. 'B' when heated with 'E' also gives back 'D'. Identify 'A' to 'E' and write equations for the reaction involved.