Which one below is a pseudohalide?

Pseudohalide ions and Pseudohalogens. There are certain monovalent negative ions made up of two or more electronegative atoms which exhibit properties similar to those of halide ions. Such ions are known as pseudohalide ions just as halide ions, pseudohalide ions have also corresponding dimeric molecules. These are called pseudohalogens and show properties similar to those of halogens.