Hierarchical Clustering can be either agglomerative, where clusters are built from the bottom up, or divisive, where clusters are split from the top down. The most common method used is _________.

Agglomerative method is the most commonly used approach in Hierarchical Clustering. It builds clusters from the bottom up, starting with individual data points and merging them into progressively larger clusters. This method allows for the creation of a dendrogram, which can be analyzed to choose the optimal number of clusters and understand the hierarchical relationships within the data.