【答案解析】The major premise— "Birds normally can fly" —is over generalized because there exist birds that are unable to fly. In this case, the first statement is a rule of thumb. Flightless birds like penguins are exceptional. So the conclusion is false.[解析] 经验法则导致了逻辑的错误。大前提本身“鸟都会飞”本身就没有做到完全归纳。