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Unit 3 A healthy life (60分钟81分) Part A 一、阅读理解(共8小题;每小题2分,满分16分) A There are an extremely large number of ants worldwide.Each individual(个体的)ant hardly weighs anything,but put together they weigh roughly the same as all of mankind.They also live nearly everywhere,except on frozen mountain tops and around the poles.For animals their size,ants have been astonishingly successful,largely due to their wonderful social behavior. In colonies(群体)that range in size from a few hundred to tens of millions,they organize their lives with a clear division of labor.Even more amazing is how they achieve this level of organization.Where we use sound and sight to communicate,ants depend primarily on pheromones(外激素),chemicals sent out by individuals and smelled or tasted by fellow members of their colony.When an ant finds food,it produces a pheromone that will lead others straight to where the food is.When an individual ant comes under attack or is dying,it sends out an alarm pheromone to warn the colony to prepare for a conflict as a defense unit. In fact,when it comes to the art of war,ants have no equal.They are completely fearless and will readily take on a creature much larger than themselves,attacking in large groups and overcoming their target.Such is their devotion to the common good of the colony that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy. | 
