Cyanogen, (CN)₂, Is Sometimes Called a Pseudohalogen

Cyanogen, (CN) ₂, is sometimes called a pseudohalogen. Why? Please select all that apply:

A) It exists as a dimer.
B) It forms similar compounds to the halogens, e.g. Cl^- and CN^- both give a white precipitate with silver nitrate.
C) The bond between the CN-CN groups can be broken by UV light.
D) It reacts with halogens readily.