练习材料：
[Day 1744 2019-07-06]
Lesson 18-1 Porpoises
There has long been a superstition among mariners that porpoises will save
drowning men by pushing them to the surface, or protect them from sharks by
surrounding them in defensive formation. Marine Studio biologists have pointed out
that, however intelligent they may be, it is probably a mistake to credit dolphins with
any motive of lifesaving. On the occasions when they have pushed to shore an
unconscious human being they have much more likely done it out of curiosity or for
sport, as in riding the bow waves of a ship. In 1928 some porpoises were photographed
working like beavers to push ashore a waterlogged mattress. If, as has been reported,
they have protected humans from sharks, it may have been because curiosity attracted
them and because the scent of a possible meal attracted the sharks.
任务配置：L0+L1+L4
知识笔记：
superstition n. 迷信; 迷信观念(或思想);
mariners n. 水手;
porpoises n. 钝吻海豚; 鼠海豚;
waterlogged adj. 水浸的; 水涝的; 水淹的; 进水满舱的; 浸满水下沉的;
练习感悟：
