Select the statement(s) about information retrieval that are incorrect. In information retrieval (IR), rare words are the same informative as common words. Assuming given a query, your IR system will return a set of documents. The recall measures among your prediction, how much percent of them are really relevant. Inverse document frequency has effects on single-term queries. BM25 is probabilistic IR model, and it is a discriminative model. The metric normalized discounted cumulative gain (NDCG) mainly considers binary relevance ratings. The dense retrieval system is more powerful than BM25; it is especially good at term matching