1. Professor Bill had began taking _______ research work when he was in high school.
A. to do B. doing C. to doing D. having done
2. Jenny was still running temperature, so she had to _______ work.
A. leave alone B. leave behind C. leave off D. leave out
3. _______ in his life, he became the proud owner of a bed which had springs and a mattress.
A. For the first time B. From time to time C. For the time being D. All the time
4. It is time that we _______ computers to the productions of iron and steel.
A. applied B. will apply C. have applied D. would have applied
5. I would have you _______ that I am a person fo some important in this company.
A. to know B. know C. knowing D. known