Storing food is common in members of the crow family. A new study tested the birds outside for this naturally occurring behaviour, which may have evolved（进化） specifically because it gives crows a survival advantage. Some crow species are known to naturally use tools to recover food. So the researchers tested whether the birds could store and recover a tool so they could get it at their food after a gap of 17 hours - something we wouldn't expect them to do naturally. But they were able to instantly select the tool out of a number of unnecessary items.
In another experiment, the researche crows to select a token（礼品券）from a number of items so that they could then exchange it for food.Again, the birds then showed that they could plan for the future using this new behaviour. This is different from all of the previous studies in future planning,which have focused on naturally occurring behaviour.For example, we know that chimpanzees select,transport and save appropriate tools for future needs.
These studies have shown that animals can plan for the future- but they leave an important question open for debate. Are animals only able to plan to use abilities that have evolved to give them a specific advantage,or can they flexibly and intelligently apply planning behaviour across various actions？ Most critics would say the former, as the animals were tested in naturally occurring behaviour.
But the new research provides the first evidence that animal species can plan for the future using behaviour that doesn't typically occur in nature. This supports the view that at least some recognitive（认知的）abilities in animals don't evolve just in response to specific problems. Instead, it suggests that animals can apply these behaviour flexibly across problems in a similar way to humans. We need to study how flexible behaviour evolved. Then we might be able to see how crows' ability to plan for the future fits in with their broader cognitive powers.



What's the new finding about some crows according to Paragraph 1？ ______

A. They can store food.
B. They can use tools to recover food.
C. They can store and recover tools.
D. They can select and store food.

What are crows trained by researchers to do when given a token？ ______

A. Reject it casually.
B. Exchange it for food.
C. Save it as their food.
D. Build a nest with it.

What can we infer about the studies that animals for the future？ ______

A. They are debatable.
B. They are disappointing.
C. They are logical.
D. They are convincing.

What can be learned about flexible behaviour in animals？ ______

A. It develops only with age.
B. It is unclear how it evolved.
C. No animals but crows benefit from it.
D. It helps plan for the future.