An organic compound $\mathrm{A}\left({\mathrm{C}}_6{\mathrm{H}}_6\mathrm{O}\right)$ gives dark green colouration with ferric chloride. On treatment with ${\mathrm{CHCl}}_3$ and $\mathrm{KOH},$ followed by acidification gives compound $\mathrm{B}.$ Compound $\mathrm{B}$ can also be obtained from compound $\mathrm{C}$ on reaction with pyridinium chlorochromate (PCC). Identify $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}.$