What kind of planet elsewhere in the universe can support life A: Those double stars' planets. B: Those planets much hotter than our earth. C: Those planets similar to the earth. D: Those planets very close to their suns.

The solar system in astronomy consists of the sun and its planets. EXCEPT （）, all the planets got their names from Greco-Roman mythology. A: Mars B: Earth C: Venus D: Jupiter

Scientists cannot _______ the existence of life on other planets.

It is hoped that man will someday inhabit other planets.

Is the space travel to other planets safe?

Which of the following does not characterize Mercury A: nearest of all planets to the sun B: extremely hot C: little known to people D: biggest of all planets

Though challenged by many people, Aczel firmly believes that ______. A: about 1 million planets in our galaxy are suitable for life B: it is very likely for life to exist on other planets C: life exists in approximately 150 billion stars in our galaxy D: there are a very large number of planets suitable for life

Ellipses (椭圆) are used to describe the motions of the planets around the sun.

在太阳系所有的行星中，哪颗行星离地球最近呢？ A: In all the planets in the solar system, which planet is closest to the Earth? B: Among all the planets in the solar system, which planet is near to the Earth? C: Of all the planets in the solar system, which planet is closest to the Earth?

中国大学MOOC:"It’s unlikely there will ever be any ________ to the argument about whether there is life on other planets.";