Up until about 2 billion years ago, the sun was 30
percent dimmer than it is now. If the sun were that dim
now, our oceans would be completely frozen.
According to fossil evidence, however, life and liquid
water were both present as early as 3.8 billion years
ago.
Which one of the following, if true, most helps to
resolve the apparent discrepancy described above?
(A) Our atmosphere currently holds in significantly
less heat than it did 3.8 billion years ago.
(B) The liquid water present 3.8 billion years ago
later froze, only to melt again about 2 billion
years ago.
(C) A significant source of heat other than the sun
contributed to the melting of ice sheets
approximately 2 billion years ago.
(D) Evidence suggests that certain regions of ocean
remained frozen until much more recently than
2 billion years ago.
(E) When large portions of the globe are icecovered,
more of the sun’s heat is reflected and
not absorbed by the earth than when only the
poles are ice-covered.
percent dimmer than it is now. If the sun were that dim
now, our oceans would be completely frozen.
According to fossil evidence, however, life and liquid
water were both present as early as 3.8 billion years
ago.
Which one of the following, if true, most helps to
resolve the apparent discrepancy described above?
(A) Our atmosphere currently holds in significantly
less heat than it did 3.8 billion years ago.
(B) The liquid water present 3.8 billion years ago
later froze, only to melt again about 2 billion
years ago.
(C) A significant source of heat other than the sun
contributed to the melting of ice sheets
approximately 2 billion years ago.
(D) Evidence suggests that certain regions of ocean
remained frozen until much more recently than
2 billion years ago.
(E) When large portions of the globe are icecovered,
more of the sun’s heat is reflected and
not absorbed by the earth than when only the
poles are ice-covered.
