The correct option is C electrophilic substitution reaction
When phenol gets converted to salicylaldehyde in the presence of CHCl3+Aq.NaOH followed by hydrolysis, the reaction is known as Reimer-Tiemann reaction. It is an electrophilic substitution reaction, reaction intermediate dichloro carbene is formed and acts as an electrophile. Hence, the correct answer is option (c).