Select total number of the acidic compounds out of given below

$\mathrm{CsOH}, \mathrm{OC}(\mathrm{OH}{)}_2, {\mathrm{SO}}_2(\mathrm{OH}{)}_2, \mathrm{Sr}(\mathrm{OH}{)}_2, \mathrm{Ca}(\mathrm{OH}{)}_2, \mathrm{Ba}(\mathrm{OH}{)}_2, \mathrm{BrOH}, \mathrm{NaOH}, {\mathrm{O}}_2\mathrm{NOH}$

Metallic oxides are known to show basic nature. On the other hand, non-metallic oxides are observed to show acidic properties. Out of the provided bases, the acidic compounds are 4 in total.