Select the incorrect statement about the carbohydrates ?

I. It has general formula,  ${\mathrm{C}}_{\mathrm{x}}{\left({\mathrm{H}}_2\mathrm{O}\right)}_{\mathrm{y}}$

II. They are hydrates of carbon.

III. The molecular formula of rhamnose  is  ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_5$ and it is not a carbohydrate.
IV. Molecular formula of acetic acid is represented as  ${\mathrm{C}}_2{\left({\mathrm{H}}_2\mathrm{O}\right)}_2$  and it is a carbohydrate.