Young as he is, David has gained ____ rich experience in ____ society.
The book is _______ that one.
The name of our country is PRC, which _____ the People’s Republic of China.
He came back late, _____ which time all the guesses had already left.
Because so many visitors are visiting our school today, some teachers have to _______ guides.
She thinks only of herself; she doesn’t _____ other people.