Let us consider a B$-$Tree of order $M,$ where $L$ is the maximum number of records per leaf node. We assume that the $B-$tree stores $N$ records.

Select one or more:

a$.$ The total cost of the Find operation is $O(lo{g}_M(\frac{N}{L})xlog\frac{M}{2})$ in the best case

b$.$ A B$-$tree requires AVL rotation so it does not degenerate

C$.$ A BST should be used instead of the B$-$tree, if all the data can fit in RAM

d$.$ The total cost of the Find operation is $O(lo{g}_{\frac{M}{2}}(2\frac{N}{L})log\frac{M}{2}+log\frac{L}{2})$ in the worst case