练习材料：
Lesson 18-3 Porpoises
This is not easy, and may require two porpoises working together. In another game, as the turtle swims across the oceanarium, the first porpoise swoops down from above and butts his shell with hisbelly. This knocks the turtle down several feet. He no sooner recovers his equilibrium than the next porpoise comes along and hits him another crack. Eventually the turtle has been butted all the way down to the floor of the tank. He is now satisfied merely to try to stand up, but as soon as he does so a porpoise knocks him flat. The turtle at last gives up by pulling his feet under his shell and the game is over.
应用配置：L0+L4
知识笔记： oceanarium/oceanarium equilibrium/ikwəˈlɪbriəm belly/bɛli
练习感悟：用时40分。内容不多，有几个难发的音也练了挺久，录了几遍，最后一版不是最快的，不过语速方面还可以。
