China recently tightened its waters controls near the Huangyan Island to prevent Chinese fishing boats from in the South China Sea.
I waved to Nancy, but she was _______ in her thought, and made no response.
With ______ help of his teachers, he made ______ great progress in his study.
I _____ in the street when someone _____ me.
The number of people who _______ invited to the meeting _____ fifty, but a number of them _____ absent for different reasons.
The early pioneers had to _____ many difficulties to settle down on the new land.