Reaction of aromatic diazonium ion where 2 N atoms are retained are called :
Retention reaction
Nitrogen retention reaction
Coupling reaction
nitrogen coupling reaction
As we have learned
Reaction of aromatic diazonium ion -
Their reactions may be divided into two groups; those which involve the liberation of nitrogen gas by another univalent group and those in which the two N atoms are retained ( coupling reactions ).
Correct option is 3.