The traditional view is ______ we sleep because our brain is “programmed” to make us do so.
______ as the main reason for the recent world-wide economic problems is the fact that the US government would hardly accept.
The Apple Company had scarcely released i-Phone ______ it became one of the best-selling electronic products.
Electrolysis(电解)is the process ______ electric current is passed through a substance to cause a chemical charge.
So much ______ by the poem for the Wenchuan earthquake that he decided to participate in the re-construction of the damaged region.
Scientists ______ SARS for several months before a major discovery was made in the field.