.
This is Sandmeyer reaction in which the diazonium group is replaced by bromine.
Ar+N2X−HBF4−−−→ΔArF.
This is Balz-Schiemann's reaction in which the diazonium group is replaced by fluorine.
Ar+N2X−C2H5OH−−−−−→ArH.
In this reaction, the diazonium group is replaced by hydrogen.
Ar+N2X−H2O−−→ArOH.
In this reaction, the diazonium group is replaced by -OH group.
Hence, option A is correct.