Answer : The oxidation state of Cl is, (+3)
Explanation :
Oxidation number : It represent the number of electrons lost or gained by the atoms of an element in a compound.
Oxidation numbers are generally written with sign (+ and -) first and then the magnitude.
The oxidation number of oxygen (O) in compounds is (-2).
The given molecule is,
Let the oxidation state of Cl be, 'x'



Thus, the oxidation state of Cl is, (+3)