The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus
fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetusprobably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetusis a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetusfed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.

3. The word precious in the passage is closest in meaning

o exact
o scarce
o valuable
o initial

词义推断:先准确定位词的位置,然后根据句子的意思推断。此句中precious valuable构成同义词。