题目内容：
根据以下材料回答第 1～4 题：In June of 1973，nine whales beached on the Florida coast．Beaching means swimmingout of the ocean onto the beach，and usually dying there．No one knows why they do it，but a number of whales beach themselves every year．Some people think beaching is an accident．
Perhaps the whales get confused．Scientists who studied the beaching of three dozen whales in Australia think the whales may have been confused by lund noises．Whales can tell where they are by sounds．They send out sounds and’listen as they travel past or bounce off objects．Two days before these thirty-six whales beached，lond guns had been fired for two hours．The lond sounds may have confused the whales．Their confusion might have caused them to wander into low water．
Whatever the reason Whales beach，it is a sad event．People try to save them，but very few beached whales live．One whale that was rescued from beaching in Florida livedfor fortyfive days．That is the longest a beached whale has ever survived．And it livedthat long only because it got attention from doctors．
All over the world，scientists．rush to whale beachings as soon as they hear about them．They hope to learn why whales beach，and how to save them．
The subject of this passage is ．
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