The pupils here_____ all kinds of exercises every day in the past few weeks.
The generation _____ makes it difficult for parents to understand their children's opinions.
If the boy had _____ the dog alone it wouldn't have bitten him.
They were so far away that I couldn't _____ their faces clearly.
Achieving a high degree of proficiency in English as a foreign language is not a mysterious _____ without scientific basis.
I must go now. _____, if you want that book I'll bring it next time.