There are v______ products on sale in the market.
__________ ( not pass) the exam, he had to work harder to pass a similar exam.
__________ ( not know) his address, I couldn't write a letter to him.
All the young workers in this large factory have to work hard __________(not lose)their work.
The new doctors stood there still, watching the patient __________ (operate)on by an expert doctor.
I can hardly stand __________ ( criticize) by all of my teachers every day.