--- Is this company ______ your elder sister once worked in?---- Yes, it is.
To be honest, I would rathermy dog out, which made so many troubles.
Jack is late again. It isof him to keep others waiting.
Jack, who pretended, heard, however, every word that was said.
The old man __________ in Tibet for two years as a volunteer teacher;it is an experience he often mentions.
Qian Xuesen tried many times _________ he found the solution to the puzzle about space technology.