—I’d like a pen which ________well.—Will this one_______?
To be honest, I would rather my dog out, which made so many troubles.
Jack is late again. It is of 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.