A fourth-grade teacher was giving her pupils a lesson on logic. Here is the situation, she said. A man is standing up in a boat in the middle of a river, fishing. He loses his balance, falls in, and begins splashing and yelling for help. His wife hears the commotion, knows that he can't swim, and runs down to the bank. Why do you think she ran to the bank? A girl raised her hand and asked, to draw out all of his savings? 小学四年级的教师正在给学生们上一堂逻辑课。她举了这么一个例子：有这样一种情况，一个男人在河中心的船上钓鱼，突然失去重心掉进了水里。于是他开始挣扎并喊救命。 他的妻子听到了他的喊声，知道他并不会游泳，所以她就急忙跑向河岸。谁能告诉我这是为什么？ 一个女生举手答道，是不是去取他的存款？