________ many times, he still couldn’t understand it.
_____ your help, we _____ complete the work in time.
I have a letter _____ to tell the headmaster that we need a room _____.
The house with the ground is valued ____ three thousand yuan, but I bought it ____ only one thousand yuan.
—Does David often come to school ____ bus?—Yes, but sometimes he comes ____ his father’s car.
Mr. Johnson starts to work very early in the morning and goes on working until late in the afternoon ________a break at midday.