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Paragraf Tamamlama 121. Soru

birinci Bu Testin Birincisi Bengu
Başarı Yüzdeniz : 100 %
121.
Some of the best discoveries are accidental. Until the 18405, for example, rubber was not a very useful material because it was too stiff in cold weather and too soft in hot weather. An American named Charles Goodyear tried to solve this problem by mixing rubber and sulphur, but the experiment failed. ……… . Though he patented the process, which we know today as "vulcanised rubber", it was so simple that many others copied it.


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