Поставьте артикль, где необходимо. a. ___ chair on which you are sitting is not comfortable. b. There is ___ man waiting to see Mr Smith. c. ___ man whom Mr Smith telephoned this morning is here now. d. I should like to find ___ good book to read tonight. e. ___ book which I am reading now is a very good one. f. Have you ___ cigarette? g. John threw away ___ cigarette he was smoking. h. Peter put ___ letter he had just received in his pocket.
2) metals are still used for most of machines, structures and instruments.
Most metals are usually found in nature as minerals or ores, where they exist in chemical combinations with other substances.
Ores are usually mined and passed to the metallurgist for refining and purification.
The ores are treated by fire or chemically by the process called smelting.
But pure metals are comparatively seldom used because they are rather expensive and their strength is generally insufficient for the purposes of to-day.
Alloys are obtained by adding various metals or non-metals to the main metallic element.