The common features among the species $CN^-,CO$ and $NO^+$ are :

Question

$\begin{array}{1 1}(a)\;\text{bond order three and isoelectronic}\\(b)\; \text{isoelectronic and weak field ligands}\\(c)\;\text{bond order two and }\pi-\text{acceptors}\\(d)\;\text{bond order three and weak field ligands}\end{array}$