Let us consider a Binary Search Tree, BST$,$ with N elements. In terms of N$,$ the complexity in time $($big$-$Oh notation$)$ of the BST operations is as follows.

Select one or more:a$.$ Inserting a new element costs $\backslash (\backslash$mathrm$\{$O$\}(\backslash$log $\backslash$mathrm$\{$N$\})\backslash )$ or $\backslash (\backslash$mathrm$\{$O$\}(\backslash$mathrm$\{$N$\})\backslash )$b$.$ Inserting a new element costs $\backslash (\backslash$mathrm$\{$O$\}(\backslash$mathrm$\{$N$\})\backslash )$ if the BST is well$-$balancedc. Inserting a new element costs $\backslash (\backslash$mathrm$\{$O$\}(\backslash$log $\backslash$mathrm$\{$N$\})\backslash )$ if the BST is well$-$balancedd. Deleting an element costs $\backslash (\backslash$mathrm$\{$O$\}(\backslash$mathrm$\{$N$\})\backslash )$ if the BST is degeneratede. Deleting an element always costs $\backslash (\backslash$mathrm$\{$O$\}(\backslash$log $\backslash$mathrm$\{$N$\})\backslash )$