I won’t allow him to make the trip alone, even if he_____ do it.

Among so many people at the party, I _______ John, one of my classmates after 20 years.

He is going into hospital to have a small __________ her knee.

There is a shortage of teachers in Western China, and it will fall on the 80s and 90s generations to           this responsibility. 

He ____ this bike for 600 yuan. Though it was a bit expensive, I think it was reasonable.