转变。

1．During the mysterious period mentioned in the passage，the Lake Huron area ________.

A．was deserted by ancient Indians

B．witnessed the start of agriculture

C．was taken up by large animals

D．began to be covered by water

答案　B　[推理判断题。从第一、二段的". . . may provide important clues to a mysterious period in North American prehistory. . . ；when humans gradually shifted from hunting large animals to fishing，gathering and agriculture"可知，B项正确。]

2．Which of the following statements is WRONG?

A．The findings of John O'Shea and his colleagues may prove a previous theory.

B．The effort that John O'Shea and Meadows made before 2010 was meaningless.

C．Some equipment was used to support the discovery.

D．John O'Shea and his colleagues didn't draw the final conclusion from visual examination.

答案　B　[细节理解题。从第三段的"In 2009 they reported finding a series of stone features that they believe were 'drive lanes' used by ancient Indian hunters. "可知，John O'Shea和Meadows之前的研究也是有成效的。]

3．What's the fourth paragraph mainly about?

A．How the wood was found.

B．Why the wood is important.

C．Preparations that were made for the discovery of the wood.

D．Conclusions the experts have made from the discovery of the wood.

答案　A　[段落大意题。本段主要交待了John O'Shea 和同事们怎样找到这块木头的。]

4．What do we know about the future plan of John O'Shea and his colleagues?

A．They will explore another lake soon.