These are the properties of a $B^{+}$ tree. In a $B^{+}$Tree, data pointers are stored only at the leaf nodes; hence, the structure of leaf nodes differs from the structure of internal nodes. Since, all data pointers are at the leaf level every key value must exist at the leaf level.
So, the correct answer is $A;B;C;D.$
PS: For option C, in a $B^+$ tree of order $p,$ an internal node can have maximum $p$ children but minimum it must have $\lceil p/2 \rceil$ children.
Reference: https://en.wikipedia.org/wiki/B%2B_tree