单选题 The author refers to the increase in animal bones in the fourth paragraph primarily in order to

• (A) demonstrate the increase of the availability of grazing mammals during the desiccation of the African landscape
• (B) suggest a reason why robust proto-humans eventually failed in the competition with Homo for animal prey
• (C) provide proof that environmental changes did indeed occur around a time of rapid evolution for Homo
• (D) explain the means by which Homo was able to make use of the appearance of the antelope and gazelle
• (E) offer evidence that with the desiccation of the African landscape, Homo's diet changed from that of the australopithecine