We won't know how the plan works till we have tried it ________.
The old man watched the young boys playing _______ basketball with _______great interest .
China ________ the developing countries in the world .
We regret ______ that the film was not worth _________.
She thought I was talking about her daughter , _____, in fact , I was talking about my daughter .
It was a pity that the great writer died _______ his works unfinished.