Questions 11 to 13 are based on the following passage.

During this century, archaeologists have discovered that trees can be a valuable tool for measuring time. In scientific terms, this method is called dendrochronology. Dendrochronology is based on the scientific discovery that (11) each year a tree grows a new layer of wood. When you cut down a tree, for example, you can see and count the layers of concentric circles. The layers vary in color and in thickness. (12) These variations are a result of differing climate conditions from year to year that affects the growth of the annual rings. Cold weather, for example，creates thinner and lighter rings while hot weather produces thicker and darker rings. All trees that grow in the same region will have roughly the same pattern of annual rings，and this can be used as a source of comparison and measurement. Early in this century, (13) archaeologists began using the rings to date ruined structures and figures built in the southwestern United States. They did this by comparing the rings of the wood found in the ruins with the rings of recently cut trees. Slowly but surely, the system was extended backwards in time to measure older ruins. The heavy forestry of the United States, coupled with the relative youth of its history, led to a fairly uncomplicated study.

 

题目

Passage 2

In this section you will hear several passages. Listen to the passages carefully and then answer the questions that follow.

Questions 11 to 13 are based on the following passage. At the end of the passage，you will be given 15 seconds to answer the questions.

Now, listen to the passage.

11. What happens during the natural growth of a tree each year?

A. Their rings become lighter in color.

B. They have one more ring of wood.

C. They become more precious.

D. Their rings get closer and closer.

12. What may lead to the differences among the rings of the same tree?

A. The weather.

B. The exposure to sunlight.

C. The nutrition provided by the soil.

D. The time span.

13. Why are the archaeologists interested in dendrochronology?

A. They can measure constructions.

B. It helps them study past society.

C. It provides a time tracing procedure.

D. They can build more buildings.

 

答案解析

Passage 2

11. B细节题。文中指出每年树木都会长粗一圈，即会多一圈年轮，故B项意思正确。

12. A细节题。文章说到树木的年轮圈各不相同，主要是由于不同的气候条件会影响 每个年轮圈的生长。故选项A是正确的。

13. C细节归纳题。文中介绍考古学家利用树木的年轮来推断美国西南部的一些遗 迹的年代，故C项表意正确。