. He is one of those who ______ very hard.
The little girl who got lost decided to remain __________ she was and waited for her mother.
Green is usually regarded as a __________ of life while red stands for joy and victory. A. symbol B. sign C, mark D. signal
It's rude __________ you to ask his salary the first time you __________ him.
We should consider the students' request __________ the school library provide more books on popular science.
—How much do you know about the 3D film technology?_ A little. Not until the hot movie Avatar __________ some about it.