Of the two brothers, Bill is ______ younger one, and he is a quiet boy, ______ that most adults like very much.
After half a year’s training, they were made entirely used ____ underwater.
Thank you very much for the trouble you have taken _________ me with my English.
Before the conference, a new problem came up __________ could speak on behalf of our group.
He dressed up and went to the party as if ___________.
Scientist are not sure about the ___________ of water on the Mars.