Mr. Smith is busy these days ________ a new book on how to develop a child’s reading skill.
Of all the plays __________ recently, none is more impressive than Tea House by Lao She.
—Is there a place __________? —I'm afraid there're no other places free at the moment.
Misunderstandings __________ from lack of social communication, unless __________ properly, may lead to serious problems.
All the branch companies are __________ the members of the family.
Even though they were much younger, we treated them __________ equals.