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3. Comprehension: Cause and effect.
Scientists who study astrobiology (天体生物学) always try to look for life in space. In recent years, they have turned their attention to Europa, one of Jupiter’s moons. Europa is a little smaller than Earth’s moon and is covered by a sheet of ice. Its surface is too cold and has too much radiation for anything to live there. Scientists want to know what is under the ice. They believe that is where life on Europa might be.
What Life Needs
For years, scientists thought all life on Earth depended on energy from the Sun. During a process called photosynthesis, plants use energy from sunlight to make food and to put oxygen into the atmosphere. Aerobic creatures use that oxygen to breathe. Sunlight also provides the warmth that life needs. Scientists believed that nothing could live in extreme temperatures. Scientists also thought that all food chains led back to plants and photosynthesis. Recent discoveries, however, have changed what scientists think about life. They have found worm - like creatures and other animals living around hydrothermal vents (深海热泉) on the ocean floor. These creatures do not depend on the Sun or plants for food and energy.
The animals living around hydrothermal vents eat bacteria that live on or below the ocean floor. The bacteria get energy through a process called chemosynthesis. Hydrothermal vents spit warm water filled with chemicals from inside the Earth. The bacteria use these chemicals as a source of food and energy.
New Possibilities
The discovery of chemosynthetic life changed the way scientists think about life in space. They no longer have to look only for places with sunlight and oxygen. Planets with oceans and hydrothermal vents might also support life. Based on these discoveries, Europa began to seem like a place where life might exist. Europa has oxygen in its atmosphere, but the oxygen does not come from photosynthesis. Europa is too far from the Sun and too cold to support photosynthetic life. Its surface temperature is usually more than 200 degrees below zero Fahrenheit. Europa does have oceans. The ice on this moon’s surface covers what looks like moving liquid water. Do these oceans have hydrothermal vents? Scientists do not yet know. If they do, the oceans of Europa might support chemosynthetic life. Only a visit to Europa would tell for sure.
(
A. It has no oxygen.
B. Its water is frozen.
C. It lacks sunlight.
D. It has no radiation.
(
A. Europa.
B. Chemosynthesis.
C. Hydrothermal vents.
D. Bacteria.
(
A. Frozen oceans.
B. Hydrothermal vents.
C. Direct sunlight.
D. Carbon dioxide.
Scientists who study astrobiology (天体生物学) always try to look for life in space. In recent years, they have turned their attention to Europa, one of Jupiter’s moons. Europa is a little smaller than Earth’s moon and is covered by a sheet of ice. Its surface is too cold and has too much radiation for anything to live there. Scientists want to know what is under the ice. They believe that is where life on Europa might be.
What Life Needs
For years, scientists thought all life on Earth depended on energy from the Sun. During a process called photosynthesis, plants use energy from sunlight to make food and to put oxygen into the atmosphere. Aerobic creatures use that oxygen to breathe. Sunlight also provides the warmth that life needs. Scientists believed that nothing could live in extreme temperatures. Scientists also thought that all food chains led back to plants and photosynthesis. Recent discoveries, however, have changed what scientists think about life. They have found worm - like creatures and other animals living around hydrothermal vents (深海热泉) on the ocean floor. These creatures do not depend on the Sun or plants for food and energy.
The animals living around hydrothermal vents eat bacteria that live on or below the ocean floor. The bacteria get energy through a process called chemosynthesis. Hydrothermal vents spit warm water filled with chemicals from inside the Earth. The bacteria use these chemicals as a source of food and energy.
New Possibilities
The discovery of chemosynthetic life changed the way scientists think about life in space. They no longer have to look only for places with sunlight and oxygen. Planets with oceans and hydrothermal vents might also support life. Based on these discoveries, Europa began to seem like a place where life might exist. Europa has oxygen in its atmosphere, but the oxygen does not come from photosynthesis. Europa is too far from the Sun and too cold to support photosynthetic life. Its surface temperature is usually more than 200 degrees below zero Fahrenheit. Europa does have oceans. The ice on this moon’s surface covers what looks like moving liquid water. Do these oceans have hydrothermal vents? Scientists do not yet know. If they do, the oceans of Europa might support chemosynthetic life. Only a visit to Europa would tell for sure.
(
C
) 1. Why did scientists initially (最初) think life could not exist on Europa?A. It has no oxygen.
B. Its water is frozen.
C. It lacks sunlight.
D. It has no radiation.
(
B
) 2. Which discovery changed how scientists think about life in space?A. Europa.
B. Chemosynthesis.
C. Hydrothermal vents.
D. Bacteria.
(
B
) 3. As a result of their discovery, what will scientists look for on Europa?A. Frozen oceans.
B. Hydrothermal vents.
C. Direct sunlight.
D. Carbon dioxide.
答案
【解析】：1. 由文章第二段“scientists thought all life...depended on energy from the Sun”及第四段“Europa is too far from the Sun...to support photosynthetic life”可知，最初科学家认为木卫二缺乏阳光，无法支持依赖太阳能的生命，故选C。
2. 第四段明确提到“The discovery of chemosynthetic life changed the way scientists think about life in space”，即化学合成生命的发现改变了看法，故选B。
3. 第四段指出科学家关注“do these oceans have hydrothermal vents”，因热泉可能支持化学合成生命，故选B。
【答案】：CBB
2. 第四段明确提到“The discovery of chemosynthetic life changed the way scientists think about life in space”，即化学合成生命的发现改变了看法，故选B。
3. 第四段指出科学家关注“do these oceans have hydrothermal vents”，因热泉可能支持化学合成生命，故选B。
【答案】：CBB
