1) Yesterday we learned how life appeared on our planet.
2) Sciencists think that 4.6 billion years ago the Earth represented a swirling mass of boiling hot rocks and gases.
3) Jason, what are you doing at such a late hour? - I am typing the results of my experiment.
4) If the matter wasn't urgent, I wouldn't have asked you to come today.
5) Peter wishes he knew more about this subject.
