Consider an empty binary search tree of height $-1.$We need to fill the following sequence of numbers in it $: 11, 12, 13, 14, 15, 16, 17.$The number of ways in which the numbers can be inserted in an empty binary search tree, such that the resulting tree has height $6,$ is _____________ $A)2$ $B)4$ $C)32$ $D)64$