1. By 5 o’clock the experiment will have been over. (by what time) 2. By the age of 41 Sophia Kovalevskaya had won recognition of mathematicians all over the world. (whose) 3. Zero concept has got many new applications in modern science and engineering recently. (what kind of) 4. Russian scientists had introduced thousands of new concepts by the end of the 20-th century. (who) 5. The students haven’t attended the course in the history of mathematics this month. (why) 6. They had obtained some equations by using mathematical terms before the teacher collected their papers. (how) 7. For a long time the major task of mathematicians has been to express ancient algebra in modern symbols. (how long) 8. By the end of the year the historian will have written four new books about the work of genii of mathematics. (how many) 9. Man’s technical progress has developed greatly. (what) 10. Most people have come across the term industrial robots. (what, who) 11. Some European mathematicians have tried to prove Fermat’s last theorem ever since it became known. (since when) 12. Pr. Smirnov’s postgraduates will have finished the experiment before he comes. (whose)