单项选择题
A．The meteors found on Earth were too young to have originated from the impacts in question.
B．The meteors found on Earth were too old to be easily dated.
C．Not enough impact events have been recorded in recent history to explain how any young meteors would have reached the Earth.
D．Impacts on Mars have been so small that scientists question how any meteors have reached the earth.
E．The age distribution of meteors found on Earth was inexplicably based toward youth.
单项选择题 Which of the following, if true, would cast most doubt on the conclusions drawn from Head's higher-resolution models（）
单项选择题 BIGOT: INTOLERANT ::（）
单项选择题 The passage suggests that which of the following is true concerning the probability that a given collision on Mars would eject fragments that will hit the Earth（）