The best way to explore _______ countryside is on _______foot.
She always come to our help when we get into trouble ____ she is very busy.
He has three brothers, ________is a doctor.
As teenagers of the 21st century, we should be ready to _____ the challenge of society.
The reason _____ they held a party was _____ it was Sue’s birthday.
--Why do you look pale today?--I was very ________my mother’s illness. I stayed awake last night.