Which of the following is non-linear molecule

Except ${\mathrm{CO}}_3^{2-}$ other choice ${\mathrm{CO}}_2,{\mathrm{CS}}_2$ and BeCI₂ have sp- hybridization and shows the linear structure while in ${\mathrm{CO}}_3^{-2}$the carbon and oxygen are bonded through a double bond which counts as "one electron pair" and two single bonded oxygens. Hence the molecule has three electron pairs and is trigonal planar geometry.

therefore it is non linear.