题目内容：

In the story of “The Crow and the Pitcher”（乌鸦和水罐）from Aesop’s Fables（伊索寓言）, a thirsty crow drops stones into a narrow jar to raise the low level of water inside so he can take a drink.

Now scientists have evidence to back up that story. New Caledonian crows actually do understand how to make water displacement work to their advantage, experiments showed. The results suggests that the birds are, at least in some aspects, as smart as first-graders, according to the study.

Researchers, led by Sarah Jelbert at the University of Auckland in New Zealand, presented six crows with tubes filled with water. Inside the tubes, a worm or pieces of meat on a piece of wood was floating, just out of reach of the crow. In front of the tubes, the researchers arranged a bunch of heavy rubber erasers that would sink, and light plastic objects that would float. The crows found out that they could drop the heavy objects into the tubes in order to raise the water level and get their snack.

However, the birds handled awkwardly in experiments in which they could choose to drop objects in either a wide tube or a narrow tube to get snack, the researchers said. Dropping objects into the narrow tube would lift the water level by a greater amount and put the treat within reach after just two drops. In contrast, it took around seven drops to raise the snack to the same level in the wide tube. The crows obviously didn’t realize this, and most of them went for the wide tube first.

Previous studies showed that chimps and human children can solve similar tasks. In a 2011 study, chimps and kids found out that they could put water into a tube to reach a peanut that was floating in a small amount of water at the bottom.

1.What does the text focus on?

A. Aesop’s prediction.    B. Crows’ intelligence.

C. The development of crows.    D. Human-animal communication.

2.How did the crows get the worm in a tube in Sarah’s experiment?

A. By dropping in the heavy erasers.    B. By removing the plastic objects.

C. By standing on the wood.    D. By breaking the tube.

3.What does the underlined part “the treat” in paragraph 4 refer to?

A. the tube.    B. The object.

C. the snack.    D. The water

4.What did the experiment with wide and narrow tubes show?

A. Crows are sensitive to surroundings.

B. Crows have the ability to recognize shapes.

C. Crows are cleverer than chimps and children.

D. Crows understand water displacement incompletely.