How many of the following are more acidic than ${\mathrm{CF}}_3\mathrm{COOH}$.
${\mathrm{CH}}_3\mathrm{COOH},\mathrm{HCOOH},{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH},{\mathrm{H}}_2{\mathrm{CO}}_3,\mathrm{HC}\equiv \mathrm{CH},\mathrm{Benzoic} \mathrm{acid},\mathrm{phenol}$

${\mathrm{CF}}_3\mathrm{COOH}$ is highly acidic because of the presence of three electronegative, F atoms in ${\mathrm{CF}}_3\mathrm{COOH}$. Hence, all given acids are less acidic than the given acid.