dichloromethyl cation(⊕CHCl2)
dichloromethyl anion(⊖CHCl2)
formyl cation(⊕CHO)
dichlorocarbene(:CCl2)
In the reaction the electrophile involved is dichlorocarbene (:CCl₂). In Reimer-Tiemann reaction, phenol in presence of NaOH reacts with chloroform to give salicyladehyde. Option D is correct.