Final answer:
In layering, the goal is to cut the cambium layer (option b), which is responsible for the secondary growth of plants and triggers new root formation for plant propagation.
Step-by-step explanation:
In the process of layering, the goal is to cut the cambium (b). The cambium is a layer of tissue in woody plants that is responsible for the secondary growth, or the increase in girth of the stem. The cambium is located between the wood (xylem) on the inside and the innermost layer of the bark (phloem) on the outside. When you cut through the cambium layer, it triggers the plant to regenerate tissue at that site, which can lead to the formation of new roots. This technique is useful for plant propagation. The cambium produces new vascular tissues, such as secondary xylem and secondary phloem, contributing to the thickening of the plant stem. The cut should be made carefully to avoid damaging the xylem and phloem which are vital for the transport of water, nutrients, and sugars in the plant.