L2：

讲座

1. What is the lecture mainly about?

A.How the Atlantic Ocean became connected to the Arctic Ocean

B.How changes in ocean circulation affected the Isthmus of Panama

C.How the formation of the Isthmus of Panama helped start an ice age

D.How tectonic plate movement might have created the Gulf Stream

2. According to the professor, what was probably the initial effect of the new land bridge between North and South America?

A.The flow of warm water increased along the eastern coast of North America

B.More rainwater began falling into the Atlantic Ocean

C.Ocean waves intensified on both sides of the land bridge

D.Trade winds appeared in the Atlantic Ocean

3. The professor notes the trade winds from Africa carry water vapor from the Atlantic to the Pacific Ocean. What does this point explain?（多选题）

A.Why there is little rainfall in certain regions of North Africa

B.Why the Pacific Ocean is less salty than the Atlantic Ocean

C.Why the Pacific Ocean is colder than the Atlantic Ocean

D.Why the density of water in the Atlantic Ocean increased

4. According to the professor, how could increased precipitation in the Northern Hemisphere have contributed to the cooling of the Arctic region?

A. It caused more heat to be trapped in the ocean.

B.It removed some carbon dioxide from the atmosphere.

C.It promoted the formation of sea ice, which reflected sunlight.

D.It allowed the ocean currents to reach the Arctic Ocean.

5. Why does the professor mention a fluctuation in the tilt of Earth’s axis?

A.To explain why ocean circulation patterns periodically change

B.To suggest a possible contributing factor to the Arctic glaciation of three million years ago

C.To suggest a reason that the ice age of three million years ago did not last long

D. To explain why periods of cooling occur at regular intervals

6. What can be inferred about the woman when she says this:

A.She realizes she is mistaken about the location of the Isthmus of Panama.

B.She disagrees with the professor on the size of the Isthmus of Panama.

C.She wants to demonstrate her knowledge of geography.

D.She is confused by the claim that the professor is making.