每天坚持默写
There has long been a superstition in the（among） mariners that porpoises will save drowning men by pushing them to the surface,or protect them from sharks by surrendering（surrounding） them in defensive formation.Marine Studio biologists have pointed out that ,however intelligent they may be ,it is probably a mistake to credit the dolphins with any motive of lifesaving.On the occasion（occasions） when they have pushed to shore an unconcious（unconscious） human being they have much more likely done it out of curiocity 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 matress.If ,as has been reported ,they have protected human beings from sharks,it may have been because curiosity attacted them and the scent of a possible meal attracted sharks.The porpoises and sharks are natural enemies.It is possible that upon that（such an） occasion a battle ensued,with sharks being driven away or killed.
Whether it （be）bird ,fish,or beast,porpoises are intrigued by（with） anything that is alive.They are constantly after turtles,who peacefully submit to all sorts of indignities.One young calf especially enjoyed raising a turtle to the surface with his snout and shoving him across the tank like an aquaplane.Almost any day a young porpoise will be seen trying to turn a 300-pound sea turtle over by sticking his snout under the edge of his shell and pushing up for dear life.This is not easy,and may require two porpoises working together.In another game,（as）a turtle swims across the oceanarium, the first porpoise swoops down from above and butts his shell with his belly.This knocks the turtle down a few（several） feet.He no sooner recover （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 finally gives up by pulling his feet under his shell and the game is over.
