When you drive the car,you can never be___careful to do it
The police _________ the mountain to ________ the murderer.
He told me that he had mailed part of the samples样本 and that the rest _____ in a few days.
He will give us a report on how to study English well, but when and where ________.
We should work together to build a society for kids, ________free from war and violence.
He slipped(溜进) into the classroom without ___________.