Help me open the brackets using the correct verb form.

  • 1. Last year our plant (produced, produces) many ceramic goods which (are used, were used) widely. 2. At first man (baked, has baked) vessels of clay in the sun. 3. Recently ce¬ramic compounds (are used, have been used) even in making steel. 4. Numerous analyses (have been carried out, had been carried out) before they stated the exact composition of this compound. 5. Now many scientists (are working, work) at the investigation of the new properties of ceramics. 6. Many new discoveries (took place, have taken place) since the last centu¬ry. 7. Last week they (analysed, analyse) crystal structure of those new materials by means of X-ray diffraction. 8. For many years considerable work (has been carried out, was car¬ried out) to convert ethylene into motor fuel. 9. Many beauti¬ful articles made of ceramics (provided, provides) man with tools even in ancient time.

  • 1. Last year our plant produced many ceramic goods which were used) widely. 2. At first man baked vessels of clay in the sun. 3. Recently ceramic compounds have been used even in making steel. 4. Numerous analyses had been carried out before they stated the exact composition of this compound. 5. Now many scientists are working at the investigation of the new properties of ceramics. 6. Many new discoveries have taken place since the last century. 7. Last week they analysed crystal structure of those new materials by means of X-ray diffraction. 8. For many years considerable work has been carried out to convert ethylene into motor fuel. 9. Many beautiful articles made of ceramics provided man with tools even in ancient time.