14. Mark's mother watches as he writes an essay. 15. Mark writes an essay for two hours. 16. Mark wrote for five essays in this month. 17. Last year Mark also wrote essays. 18. Mark wrote an essay when he arrived. 19. Mark wrote an essay for a long time, when they came to his friends. 20. Mark has written an essay before his parents arrived. 21. By the end of the month, Mark wrote five works. 22. While the mother brand will plant the rose, he will write an essay. 23. By the time the parents of Mark will come home, he will write a composition for two hours.
In the late 1970s, scientists detected “holes” in the ozone layer above the South and North Poles.
Did scientists detect “holes” in the ozone layer above the South and North Poles in the late 1970s?When did scientists detect “holes” in the ozone layer above the South and North Poles?Did scientists detect “holes” in the ozone layer above the South and North Poles in the late 1970s or in the late 1980s?In the late 1970s, scientists detected “holes” in the ozone layer above the South and North Poles, didn't they?At midnight, we were still driving through the desert.
Were we still driving through the desert at midnight?When were we still driving through the desert?Were we still driving through the desert at midnight or at midday?At midnight, we were still driving through the desert, weren't we?