题目内容：

    Over a hundred years ago in 1911, something strange was found in the glaciers of Antarctica. Grilffith Taylor—an Australian geologist, had discovered a blood red steam pouring out of the ice cascades（瀑布）of Talor Glacier! Popularly known as the Blood Falls, scientists had not been able to find the reason behind the blood red liquid flowing through the ice---until recently. The mystery of the Blood Falls had finally been solved.

When these falls were first discovered, scientists had believed that the red colour came from a large amount of red algae（海藻）concentrated in the water. Red algae contain a pigment（色素）which reflects red light, making the algae appear red.

This theory made sense, until it was later found that algae do not play a part in the red color of the flowing liquid at all. What really causes Talor Glacier’s waters appear blood red, is the presence of iron oxide in the liquid. The waters of the blood falls are rich in salt and iron content, and when this water comes in contact with the air, it turns red—just like rust! The water in these falls is often referred to as “brine” by scientists because of the high salt content in the water.

This reasoning behind the red colors of the falls was found back in 2003. However, the entire mystery had not yet been solved. How is it then, that the Blood Falls are not frozen?

Researchers at the University of Colorado and University of Alaska found that inside the glacier, there was a network of channels and reservoirs that move the water around. Salt water has a lower freezing temperature. In addition, when any substance undergoes a change in state, it gives off heat. Therefore, the brine actually warm itself up while it’s freezing! How this works, is that when the brine is flowing through the Talor Glacier, some of it does freeze. As a result of changing state from liquid to ice, the brine gives off heat. This heat is enough to keep the rest of the rest of the brine in liquid form, which is why it flows out of the glacier.

Incredible new chemistry facts found, any mystery solved!

1.According to the text, the red algae theory was once considered ________.

A.ridiculous B.reasonable

C.impractical D.complex

2.Why does the Blood Falls look red in colour?

A.Because there is too much salt and iron in its water.

B.Because its liquid is rich in red algae.

C.Because the following liquid reflects and sunlight

D.Because the air is thin and rare in Antarctica.

3.What is the main reason for the Blood Fall’s not freezing?

A.The water continued flowing constantly.

B.There is too much salt in the water.

C.The brine gives off heat while freezing

D.Temperatures aren’t high enough for flowing water.

4.What is the passage mainly about?

A.The discovery of the blood glacier.

B.The birth of the Talor Glacier.

C.The flowing red water in Antarctica.

D.The mystery of the Blood Falls.