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【单选题】

People once widely believed that intelt life existed on Mars.The 19th-century discovery of what appeared to be geometric designs cut across the suce was taken as evidence.The lines were thought to have been a system of cs that had been built to irrigate the suce.It is now clear that 'cs'—perhaps the most spectacular geologic features of Mars—are natural valleys where ancient rivers once flowed.
Another fragmented idea concerns the planet's seasonal changes in color.Once attributed to the rapid spread of some life-form, these shifts are now known to develop from the movement of fine dust in the atmosphere.
By the close of the 20th century none of the many experiments conducted by spacecraft had ever found persuasive evidence of life.Nevertheless, speculation continued over the existence of some form.of life, in either the present or the past.In 1996 scientists discovered organic compounds and minerals in a meteorite(陨石), consisting of Martian rock, that collided with Earth around 11,000 B.C.These compounds suggest that Mars may have been inhabited by organisms more than three billion years ago.
Why did people in the 19th century believe the existence of intelt life on Mars?

A.
Because the suce of Mars seemed to be geometric.
B.
Because the lines were drawn across the suce of the planet.
C.
Because a system of cs was thought to be there.
D.
Because it was the Martians that built the cs.
题目标签:陨石
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【单选题】People once widely believed that intelligent life existed on Mars. The 19th-century discovery of what appeared to be geometric designs cut across the surface was taken as evidence. The lines were thou...

A.
The meteorite containing organic compounds is part of Mars.
B.
A Martian rock struck Earth about 11,000 years ago.
C.
The organisms came back to life after the collision with Earth.
D.
The inhabiting organisms appeared more than three billion years ago.

【单选题】People once widely believed that intelligent life existed on Mars. The 19th-century discovery of what appeared to be geometric designs cut across the surface was taken as evidence. The lines were thou...

A.
the minor geologic characteristics of Mars
B.
natural valleys on the surface of Mars
C.
rivers that have kept flowing since ancient times
D.
a system that irrigates the whole surface

【单选题】People once widely believed that intelligent life existed on Mars.The 19th-century discovery of what appeared to be geometric designs cut across the surface was taken as evidence.The lines were though...

A.
Because the surface of Mars seemed to be geometric.
B.
Because the lines were drawn across the surface of the planet.
C.
Because a system of canals was thought to be there.
D.
Because it was the Martians that built the canals.

【单选题】For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic. Columbus went west to look for better trade routes to t...

A.
To find out if life ever existed there.
B.
To see if humans could survive there.
C.
To prove the feasibility of large-scale space ventures.
D.
To show the leading role of science in space exploration.

【单选题】For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic. Columbus went west to look for better trade routes to t...

A.
to display their country"s military might
B.
to accomplish some significant science
C.
to find new areas for colonization
D.
to pursue commercial and state interests