The first oxidation product of the following alcohol is a ketone with the same number of carbon atoms. 

Ketone is generated when secondary alcohols and potassium dichromate combine. Because acidified potassium dichromate is a very effective oxidising agent and can remove hydrogen from alcohol, it can oxidise alcohol to ketone.
The reaction can be expressed as follows:
${\text{CH}}_3{\text{CH(OH)CH}}_3\stackrel{{\text{K}}_2{\text{Cr}}_2{\text{O}}_7}{\to }{\text{CH}}_3{\text{COCH}}_3$
Thus, the compound is also known as dimethyl ketone or propanone. It is the first ketone in the series and is frequently referred to as acetone.
Therefore, the correct option is option (C) ${\text{CH}}_{\text{3}}{\text{CH(OH)CH}}_{\text{3}}$.