16．Homing pigeons are placed in a training program from about the time they are twenty-eight days of age．They are taught to enter the loft（阁楼） through a trap and to exercise above and around the loft and gradually they are taken away for short distance in wicker baskets and released．They are then expected to find their way home in the shortest possible time．
In their training flights or in actual races，the birds are taken to prearranged distant points and released to find their way back to their own lofts．Once the birds are liberated，their owners，who are standing by at the home lofts，anxiously watch the sky for the return of their entries．Since time is of the essence （本质） the speed with which the birds can be induced to enter the loft trap may make the difference between gaining a win or a second place．
The head of a homing pigeon is comparatively small，but its brain is one quarter larger than that of the ordinary pigeon．The homing pigeon is very intelligent and will continue to the point of stubbornness （顽强）；some have been known to fly a hundred miles off course to avoid a storm．
Some homing pigeon experts claim that this bird is gifted with a form of built-in radar（雷达） that helps it find its own loft after hours of flight，for hidden under the head feathers are two very sensitive ears，while the sharp prominent （突出的） eyes can see great distances in daytime．
Why do homing pigeons fly home？They are not unique in this inherent skill； it is found in most migratory birds（迁徙，候鸟），in bees，ants，toads and even turtles，which have been known to travel hundreds of miles to return to their homes．But in the animal world，the homing pigeon alone can be trusted with its freedom and trained to carry out the missions that people demand．
51．What is the purpose of the passage？B
A．To convince the reader to buy a homing pigeon．
B．To inform the reader about homing pigeons and their training．
C．To protect homing pigeons against the threat of extinction．
D．To encourage the owners of homing pigeons to set the birds free．
52．According to the passage，what happens to homing pigeons when they are about a month old？C
A．They are kept in a trap． B．They enter their first race．
C．They begin a training program． D．They get their wings clipped and marked．
53．According to the passage，what is the difference between a homing pigeon and an ordinary one？D
A．The span of the wings． B．The shape of the eyes．
C．The structure of the feathers． D．The size of the brain．
54．Why does the author mention bees，ants，toads and turtles in the last paragraph？C
A．To describe some unusual kinds of pets．
B．To measure distances traveled by various animals．
C．To compare their home-finding abilities with those of homing pigeons．
D．To interest the reader in learning about other animals．
分析 本文主要讲述信鸽以及它们如何训练找回自己的家的．
解答 BCDC
51 B 主旨大意题． 通读全文可知本文主要讲述信鸽以及它们如何训练找回自己的家的，故选B．
52 C 细节题． 根据文章第一 段Homing pigeons are placed in a training program from about the time they are twenty-eight days of age． 可知信鸽在28天大的时候就开始进行了训练计划，故选C．
53 D 细节题． 根据文章第三 段its brain is one quarter larger than that of the ordinary pigeon． 可知信鸽的脑子比普通的大四分之一，故选D．
54 C 细节题． 根据文章最后一 段 it is found in most migratory birds（迁徙，候鸟），in bees，ants，toads and even turtles，which have been known to travel hundreds of miles to return to their homes．可知列举的动物也能旅行几百英里回到自己的家园，但是与信鸽不同，故选C．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
