An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans(the walking whale that swam) lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetusbut 9 million before Basilosaurus.The fossil luckily includes a good

portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans. The structure of the backbone shows, however, that Ambulocetus
swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetusmay have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea.

9. Why does the author use the word luckily in mentioning that the Ambulocetus natansfossil included hind legs?

o Fossil legs of early whales are a rare find.
o The legs provided important information about the evolution of cetaceans.
o The discovery allowed scientists to reconstruct a complete skeleton of the whale.
o Until that time, only the front legs of early whales had been discovered.

推断题:"lucky?"可以用排除法,选项3reconstruct, 选项4"only"都是敏感词汇,原文中不曾出现类似的表述,所以可以直接排除。1fossil leg表述不是很准确,如果是hind leg就可以考虑。所以综合以上分析,选项2是最为贴切的。