According to paragraph 6, which of the following statements challenges the view that hunting by humans caused the extinctions of North American megafauna? A. The Clovis sites that contain the remains of mammoths were settled by humans long after the extinctions occurred. B. Only a few of the Clovis sites are located near known mammoth habitats. C. No archaeological evidence of extinctions has been found at Clovis sites since 1982. D. The number of mammoth remains found at Clovis sites is smaller than would be expected if hunting by humans had caused the extinctions.