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