VI. B. A) Insert articles where necessary

1. Wood is … most ancient structural material. 2. Wood has … certain disadvantages. 3. Wood is unsuitable for … fire-proof buildings. 4. Stone belongs to one of … oldest building materials. used by man. 5. Gravel and sand are widely employed as … aggregates in the production of artificial building materials. 6. Clay products and concrete are … examples of artificial building materials. 7. Concrete is … mixture of cement, sand, crushed stone and water. 8. We use main building materials for … bearing structures. 9. At … end of the 19^th and the beginning of the 20^th centuries people began to utilize various artificial stone materials.

b) Insert prepositions where necessary

1. Materials that are used … structural purposes should be hard, durable, fire-resistant. 2. Wood is unsuitable … fire-proof buildings. 3. Stone belongs … one of the oldest building materials. 4. Stone is characteristic … many properties. 5. Owing … its high building qualities natural stone is widely employed in modern building for facing of fronts and interiors of buildings. 6. Gravel and sand are widely employed … paving materials. 7. Rocks are employed in the production of building materials, … instance, Portland cement. 8. Clay products and concrete are examples … artificial building materials. 9. Steel has come … general use with the development of industry. 10. All building materials are divided … three main groups. 11. We use main building materials … bearing structures. 12. … the end of the 19^th centuries people began to utilize various artificial stone materials.

c) Choose the right variant

1. Materials that (is /are) used for structural purposes should be hard, durable, fire-resistant. 2. Wood is the (more / most) ancient structural material. 3. Wood (has / have) certain disadvantages. 4. Stone belongs to one of the oldest building materials (uses / used) by man. 5. Bricks (are / were) known many thousands of years ago. 6. Gravel and sand (is / are) widely employed as aggregates. 7. (Building / Binding materials are used for joining different planes. 8. For the (exterior / interior) finish of the buildings we use secondary materials.

VI. C. Answer the questions

1. What should materials that are used for structural purposes be? 2. What are natural building materials? 3. What is wood characteristic of? 4. What disadvantages does wood have? 5. What properties is stone characteristic of? 6. Where is it employed? 7. What materials are employed as aggregates? 8. Where are rocks employed? 9. What are artificial building materials? 10. What three main groups are all building materials divided into? 11. What are main building materials used for? 12. What are binding materials used for? 13. What are secondary materials used for? 14. What new materials did people begin to utilize at the end of the 19^th and the beginning of the 20^th centuries?

VI. D. Speak on the classification and usage of building materials and their properties using: As is known, in fact, I should say, it should be noted, to divide into

Table 1