Pollen never deteriorates. It is one of the few naturally secreted substances that last indefinitely.

　　花粉永远不会变质，是自然界中少有的几种可以无限期存在的物质之一。



　　Migrating geese fly in a V formation to save energy. A goose's wings churn the air and leave an air current behind. In the flying wedge, each bird is in position to get a lift from the current left by the bird ahead. It is easier going for all, except the leader. During a migration, geese are apt to take turns in the leading position.

　　迁移中的大雁群成V字队形飞是为了节省能量。一只大雁的翅膀扇动空气，在身后留下一股气流。在飞行的楔行队列中，每一只大雁都得到前面的雁产生的气流的升力。这样，除了领队以外，所有的雁飞起来都省力些。一次迁移飞行中往往有几只大雁轮流领飞。

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