10. Why k-nearest neighbor is lazy learning algorithm? (2 points) 11. When does k-means clustering stop creating or optimizing clusters? (4 points) 12. Suppose Cluster1 contains 3 objects {2,5,9} and Cluster2 contains 3 objects {15,16,18). If we are applying single linkage clustering, what will be the distance between two clusters? (2 points) 13. What is the use of Link analysis? (2 points) 14. How can classification and clustering be used in an IR system? (Give an example for each one) (4 points) 15. List three key elements shared by most of retrieval models (such as BM25 and language models) we have learned in class. (6points)