The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
The layer of tissue present in the stems and roots of plants that help in plant growth is called as the cambium. These actively dividing cells forms a layer between xylem and phloem tissues and is responsible for the secondary growth, which results in the increase in girth of the tree. There are three types of cambium present, cork cambium, unifacial cambium and vascular cambium. The vascular cambium is made up of fusiform initials that are axially oriented and ray initials. Thus, the correct answer is option B.