Scientists_____ hard to find a new and effective treatment which _____most dangerous diseases.

In two years, many of the students  ________ and then we _______ difficulty in keeping our school business going.

The women _______ for almost ten minutes when the teacher suddenly ________ the classroom.

It is five months since we _______ over this company.

When I ______into him on the street, he said he ______ abroad for business affairs that evening.

The government ______ action into increasing taxes as soon as they _____ by the authorities.

Don't you think it _______ time we _______ typing the report?

China ______ greatly in terms of its cultural values over the past five years.

I feel lucky to have found a well-paid job on time, otherwise ______ for a job now.

I ________ quite a low grade in the English exam, so I ________ harder and harder.