The correct answer is: A and B.
The natural bed of a stone is the distinct plane of division along which it can easily be split. This plane is usually parallel to the layers of sediment that were deposited to form the rock. In sedimentary rocks, the natural bed is often called the bedding plane. The natural bed of igneous rocks is not as well-defined as in sedimentary rocks, but it can be seen in some cases where the rock has been intruded into other rocks.
Option C is incorrect because the natural bed of igneous rocks is defined, although it may not be as well-defined as in sedimentary rocks.
Option D is incorrect because only A and B are correct.