The correct answer is D.
In K-means clustering, the cluster centroid is the mean of all the points in the cluster. To find the cluster centroids for the second iteration, we first need to find the mean of each cluster. The mean of cluster C1 is $(2+4+6)/3=4$, the mean of cluster C2 is $(0+4+2)/3=2$, and the mean of cluster C3 is $(5+9)/2=7$. Therefore, the cluster centroids for the second iteration are $(4,4)$, $(2,2)$, and $(7,7)$.
Here is a step-by-step solution:
- Find the mean of each cluster.
Cluster C1: $(2+4+6)/3=4$
Cluster C2: $(0+4+2)/3=2$
Cluster C3: $(5+9)/2=7$
- The cluster centroids for the second iteration are $(4,4)$, $(2,2)$, and $(7,7)$.