Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of :

The main product of the following reaction is

$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $${C_6}{H_5}C{H_2}CH\left( {OH} \right)CH{\left( {C{H_3}} \right)_2}\buildrel {conc.{H_2}S{O_4}} \over \longrightarrow \,?$$

Toluene is nitrated and the resulting product is reduced with tin and hydrochloric acid. The product so obtained is diazotised and then heated with cuprous bromide. The reaction mixture so formed contains

In the following sequence of reactions, the alkene affords the compound ‘B’
CH₃ - CH = CH - CH₃ $$\buildrel {{O_3}} \over \longrightarrow $$ A $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{Zn}^{H{}_2O}} $$ B
The compound B is