The Japanese Macaca monkey has been studied in the wild for over 50 years. In 1952, on one small Japanese island, scientists dropped some 36 dirt for the monkeys. The monkeys liked their taste, but they found the dirt 37 .
One clever 18-month-old monkey 38 the problem by washing the sweet potatoes in a nearby river, She taught this to her mother. Her 39 also learned this new way and they taught their mothers too.
All the younger monkeys 40 learned to wash the dirty sweet potatoes to make them 40 to eat. But many found it very hard to learn this and still ate the 42 sweet optatoes.
Then something very 43 . In the autumn of 1958, scientists found that the monkeys on other nearby 44 began washing their sweet potatoes too. Scientists still don’t fully understand how this knowledge was 45 from one island to another.
A．sweet potatoes B．green plants C．hard stones D．fresh nuts
A．beautiful B．terrible C．difficult D．interesting
A．find B．reach C．solve D．understand
A．children B．brothers C．sisters D．friends
A．quietly B．esily C．angrily D．awfully
A．nicer B．smaller C．lighter D．drier
A．small B．large C．new D．dirty
A．took on B．took off C．took place D．took away
A．trees B．islands C．beaches D．rivers
A．lost B．dropped C．passed D．left