1. This man is a writer. He writes books. He has been writing books since he was a young man. He has already written eight books. 2. What have you been doing here since morning? 3. Lena is a very good girl. She always helps her mother about the house. Today she has been helping her mother since morning. They have already washed the floor and dusted the furniture. Now they are cooking dinner together. 4. He is running now. He has been running for ten minutes without any rest. 5. What are they doing now? — They are working in the reading room. They have been working there for three hours already. 6. Where is he now? — He is in the garden. He is playing volleyball with his friends. They have been playing since breakfast time. 7. I live in St. Petersburg. I have been living in St. Petersburg since 1990. 8. This is the factory where my father works. He has been working here for fifteen years. 9. Have you found your notebook? — No, I am still looking for it. I have already been looking for it for two hours, but have not found it yet. 10. You have been playing with a ball for three hours already. Go home and do your homework. 11. Wake up! You have been sleeping for ten hours already. 12. I have been waiting for a letter from my cousin for a month already, but have not received it yet. 13. She has already been doing her homework for two hours; but she has not done half of it yet. 14. I have been waiting for you since two o'clock. 15. What are you doing? – I am reading. I have been reading for two hours already. I have already read sixty pages. 16. It is difficult for me to speak about this opera as I have not heard it. 17. I have just received a letter from my granny, but I have not received any letters from my parents yet. 18. The weather is fine today. The sun has been shining ever since we got up. 19. Every day I wind up my watch at 10 o'clock in the evening. 20. Come along, Henry, what are you doing now? I have been waiting for you for a long time. 21. Where are your gloves? — I have put them into my pocket. 22. I am staying with some American friends in Chicago. I have been staying with them for two weeks now. I am having a great time here, I am taking the opportunity to improve my English. I have already seen the towering skyscrapers of Chicago which are reflected in the rippling water of Lake Michigan. I have just taken a picture of Chicago's Sears Tower which rises 1,707 feet and provides a panoramic view from the skydeck. 23. I am going to give that cat some food. I am sure it is starving. — But Jane has already fed the cat. You needn't do it.

Это упражнение представляет собой серию предложений, направленных на практику Present Perfect, Present Perfect Continuous, а также Present Simple и Present Continuous — основных времен в английском языке, используемых для описания действий, происходящих в настоящем или начавшихся в прошлом и продолжающихся до настоящего момента. Разберу каждое из них с пояснением:

1. "This man is a writer. He writes books. He has been writing books since he was a young man. He has already written eight books."
   Здесь использованы Present Simple («He writes books») — привычное действие, Present Perfect Continuous («He has been writing…») — процесс, длящийся с молодости, и Present Perfect («He has already written…») — результат (8 книг уже написано).

2. "What have you been doing here since morning?"
   Используется Present Perfect Continuous — подчеркивает длительность действия с утра.

3. "Lena is a very good girl..."
   Комбинация Present Simple (общая характеристика Лены), Present Perfect Continuous (действие с утра), Present Perfect (уже сделали работу) и Present Continuous (сейчас готовят ужин).

4. "He is running now. He has been running for ten minutes without any rest."
   Сначала — текущее действие (Present Continuous), затем — его длительность (Present Perfect Continuous).

5. "What are they doing now? — They are working..."
   Сначала спрашивается о текущем действии (Present Continuous), затем подчеркивается его длительность (Present Perfect Continuous — «for three hours already»).

6. "Where is he now? — He is in the garden..."
   Используется Present Continuous для описания текущего действия и Present Perfect Continuous для подчеркивания, как долго оно длится.

7. "I live in St. Petersburg..."
   Здесь — Present Simple (общеизвестный факт) и Present Perfect Continuous (указание на длительность проживания с 1990 года).

8. "This is the factory where my father works..."
   Present Simple — текущее место работы, Present Perfect — подчеркивается стаж (15 лет).

9. "Have you found your notebook?..."
   Комбинация Present Perfect (результат — «нашёл?») и Present Perfect Continuous (процесс поиска).

10. "You have been playing with a ball for three hours already..."
    Present Perfect Continuous — подчеркивается чрезмерная длительность действия.

11. "Wake up! You have been sleeping for ten hours already."
    Опять же, длительность — Present Perfect Continuous.

12. "I have been waiting for a letter..."
    Ожидание длится месяц — используется Present Perfect Continuous, также Present Perfect с отрицанием (письмо не получено).

13. "She has already been doing her homework for two hours..."
    Опять же, длительность + результат (мало сделано) — сочетание Present Perfect Continuous и Present Perfect с отрицанием.

14. "I have been waiting for you since two o'clock."
    Классическое использование Present Perfect Continuous с указанием начала действия.

15. "What are you doing? – I am reading..."
    Комбинация времен: Present Continuous (сейчас читаю), Present Perfect Continuous (читаю уже 2 часа), Present Perfect (результат — 60 страниц прочитано).

16. "It is difficult for me to speak about this opera..."
    Используется Present Perfect в отрицательной форме — не слышал, следовательно, не могу судить.

17. "I have just received a letter from my granny..."
    Present Perfect с «just» и «yet» — недавнее действие и отсутствие результата.

18. "The weather is fine today..."
    Present Perfect Continuous — солнце светит с самого утра.

19. "Every day I wind up my watch at 10 o'clock..."
    Present Simple — регулярное действие.

20. "Come along, Henry..."
    Текущее действие (Present Continuous) + ожидание (Present Perfect Continuous).

21. "Where are your gloves? — I have put them..."
    Present Perfect — недавнее действие, имеющее значение в настоящем.

22. "I am staying with some American friends..."
    Комбинация Present Continuous (временное действие), Present Perfect Continuous (две недели уже у них), Present Perfect (результаты — видел, сфотографировал).

23. "I am going to give that cat some food..."
    Ситуация показывает план ("going to"), но вмешивается факт из Present Perfect — кошку уже покормили.

Вывод: Это упражнение демонстрирует, как грамотно использовать Present Simple, Present Continuous, Present Perfect и Present Perfect Continuous в зависимости от ситуации: для описания регулярных действий, текущих процессов, завершённых действий с результатом и длительных действий, начавшихся в прошлом и продолжающихся до настоящего.