托福阅读：TPO2(The Origins Of Cetaceans)原文及答案

　　1. In paragraph 1, what does the author say about the presence of a blowhole in cetaceans?

　　It clearly indicates that cetaceans are mammals.

　　It cannot conceal the fact that cetaceans are mammals.

　　It is the main difference between cetaceans and land-dwelling mammals.

　　It cannot yield clues about the origins of cetaceans.

　　2. Which of the following can be inferred from paragraph 1 about early sea otters?

　　It is not difficult to imagine what they looked like

　　There were great numbers of them.

　　They lived in the sea only.

　　They did not leave many fossil remains.

　　Paragraph 3: 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. Pakicetus probably 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 Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed 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 to

　　Exact

　　Scarce

　　Valuable

　　Initial

　　4. Pakicetus and modern cetaceans have similar

　　Hearing structures

　　Adaptations for diving

　　Skull shapes

　　Breeding locations

　　5. The word it in the passage refers to

　　Pakicetus

　　Fish

　　Life

　　ocean