Our monitor, ______ it clear to us that he didn’t want to waste time playing computer games, left the Internet bar quickly.
After the age of 50 people often _____________ their individual ambitions.
He is a key ____________ in the murder so we must protect him from all kinds of danger.
Russia is _________ on the north of China.
Lately some scientists are experimenting ___________ white mice to ____________ this kind of medicine.
When the reached the top of the hill ,they _______________ so they had to stop for a rest.