1) Do not distrub him. He ... an experiment (make, is

1) Do not distrub him. He ... an experiment (make, is making, makes)
2) When ... the radio invented? (did, is, was)
3) Vacuum tubes ... according to the number of electrodes (is classified, are classified, classified)
4) Great success ... is space research (have been achieved, has been achieved, has achieved)
5) Students usually ... exams at the end of the term (are having, has, have)
6) When I came to them yesterday, they ... a transistor (were constructing, constructed, construct)
7) She ... already ... her work (finished, has finished, have finished)
8) Lectures ... by highly qualified teachers (is delivered, are delivered, are delivering)
9) George ... the university last year (has entered, enters, entered)
10) The problem ... by the professors in a month (investigated, will investigate, will be investigated)