Final answer:
Dendrochronology, the study of tree rings, is a method of numerical dating that gives exact ages by counting the secondary xylem in tree rings. Other options listed relate to relative dating instead.
Step-by-step explanation:
The method of numerical dating among the options provided is b. dendrochronology (tree rings). Dendrochronology is a scientific method that dates the age of trees by counting their annual growth rings, specifically looking at the secondary xylem. This technique can provide precise and quantifiable dates for the wood in question, which is essential for understanding and documenting past climatic events, archaeological sites, and ecological patterns. In contrast, the other options listed, such as igneous intrusions, succession, unconformities, and stratigraphic columns, are used in relative dating, which only provides information about the order of events, not their exact dates.