to apologize; connection; detail; to introduce; introductory; impossible; impression; impressive; nasty (2); to offer; offer; possibility (2); to postpone; postponement; to puzzle (2); to realize (2); solution; to solve; to suggest; suggestion.

1. In physics as in chemistry there are problems which have not been ... to this day. 2. The ... of the human mind have not yet been studied properly. 3. He didn't ... his mistake until it was too late. 4. To be frank, her silence ... me; it was not at all like her to let such things pass unnoticed. 5. It was much later that I came to realize that the first ... was hardly ever correct. 6. The secretary was most helpful, in fact she herself ... to get in touch with the railway station and arrange for the tickets to be delivered the same day. 7. He phoned to ... for the misunderstanding saying it had all been his fault. 8. With the little time we have, it's no use going into ... . 9. It was at the professor's ... that some important changes were ... into the program of studies. 10. It was a promising ... and well worth thinking over. 11. You should not have made that remark. It sounded a bit ... . 12. It was agreed that the discussion should be ... for a couple of days. 13. He spent his days among books looking for a possible ... to the problem. 14. The bank clerk was extremely apologetic, yet firm, saying that no further ... of payments could be made. 15. I was blind not to have seen the ... between those two facts much earlier. 16. We were all ... at his behaviour, to say the least it was a little funny. 17. It was my friend who ... that the ... talk at the conference should be given by Professor Nikitin. 18. It took her some time to ... that there was something behind the question and it wasn't half as innocent as it sounded. 19. The house was badly in need of repairs, yet he had no ... to do anything about it at the moment. 20. He was greatly displeased to hear about my refusal to take part in the game, in fact he was quite ... about it. 21. Finding it ... to make his opponents see his point, he gave up. 22. The Pushkin Museum of Fine Arts has an ... collection of paintings by Gauguin.