Suppose that we have four observations, whose pairwise dissimilarities are given below

d(1,2) = 0.3

d(1,3) = 0.4

d(1,4) = 0.7

d(2,3) = 0.5

d(2,4) = 0.8

d(3,4) = 0.45

For instance, the dissimilarity between the first and second observations is 0.3, and the dissimilarity between the second and fourth observations is 0.8. Apply hierarchical clustering on these four observations using single linkage. Suppose that we cut the dendrogram obtained from the hierarchical clustering such that two clusters result. Which observations are in each cluster? We use expressions like (1,2) to indicate the first and the second observations are in one cluster.

		(1,2,3) and (4)
		(1,2) and (3,4)
		(1) and (2,3, 4)
		(1,3) and (2,4)