单项选择题

According to Christopher McKay, the possibility of transforming Mars______.

A．could occur only in science fiction stories
B．will not begin for hundreds, even thousands, of years
C．is completely impractical
D．could be started in 40 to 50 years

<上一题目录下一题>

热门试题

单项选择题

Which of the following is NOT listed by the author as a characteristic of the planet Mars that would make colonization difficult

A．There is little liquid water.
B．Daytime temperatures are dangerously high.
C．The Sun's rays are deadly.
D．Nighttime temperatures are extremely low.

单项选择题

With which of the following is the passage primarily concerned

A．The possibility of changing the Martian environment.
B．The challenge of interplanetary travel.
C．The advantages of establishing colonies on Mars.
D．The need to study the Martian ecology.