26. For an information retrieval system, what is the purpose of using RPrecision metric? A. To measure the system's ability to retrieve all relevant documents in the corpus. B. To evaluate the system's performance in retrieving a fixed number of relevant documents. C. To assess the precision of the system at specific cutoff points in the ranked output. D. To determine the recall of the system without considering the total number of relevant documents. 27. In document retrieval, what is the role of markup languages like HTML and XML? A. To enhance the computational complexity of parsing documents. B. To structure and tag the content of documents, facilitating information retrieval. C. To secure the transmission of documents over the network. D. To reduce the storage space required for documents. 28. In the context of text classification, which of the following is an unsupervised technique? A. Naive Bayes classification B. Decision tree learning C. Bisecting K-means clustering D. Support Vector Machine (SVM) E. Rocchio