Поставить глаголы в правильную форму. 12. He _____ (not/ hear) the thunder during the storm last night because he _____

12. He did not hear the thunder during the storm last night because he was sleeping. 13. We hope that scientists will find solutions to our most urgent problems. 14. By next decade people will have created more efficient purification equipment. 15. What do geologists study? 16. There isn’t a cloud in the sky. It is a lovely day. 17. This time last year I was swimming in the Black Sea. 18. They are working at a chemical laboratory now. 19. In 1974, scientists did not predict an earthquake in China. 20. They were carrying out an experiment from ten till twelve o’clock in the morning. 21. He had solved this problem by 10 o’clock yesterday.