In Preorder 1st element is root and everything to left of it in inorder is in LST and right is in RST.
So A is root with BC in LST and D in RST. Option A,C eliminated.
From BC, in preorder B is first so it should be the root. B is elminnated.
So answer is D.
Also as C is after it in inorder it should be in RST(with B as root). So D would be correct.