1. He usually (to leave) his office at seven o'clock, but this week he (to work) later.
2. They don't go (not to go) to the cinema very often but when they (to go), they (to prefer) comedies.
3. These two sisters already (to speak) four foreign languages. Now they (to learn) a fifth.
4. He usually (to get up) about seven o'clock, but this month he (to be) on holiday and so he (to get up) later.
5. My dog usually (to bark) at the postman - but look at that! For once, he (to be) friendly to the poor man.
6. They left for England this morning. I (to wonder) whether they (to travel) by air or by train.
7. I usually (to write) my letters on Sunday but I (to write) this week's letters today because this coming Sunday we (to go) out.
8. I (to want) to speak to the maids at once, please. You (to know) where they (to be)? - Yes, Mary (to prepare) dinner, and I (to think) that Helen (to set) the table in the dining-room.
9. The house (to smell) unpleasant because we (to have it repainted).
10. She (to have) her birthday party tomorrow and she (to look forward) to it very much.
11. Children always (to look forward) to their birthdays.
12. He (to walk) very slowly because the bottle which he (to carry) (to hold) nitroglycerine, and nitroglycerine (to explode) if it (to be shaken).
13. I (to see) that you (to become) impatient with me, but I (to try) my best to do it properly.
14. I (to smoke) a lot these days because I (to study) for my final exams.
15. I (not to like) garlic when I (to smell) it but I (to love) it when I (to taste) it.

1. He usually leaves his office at seven o'clock, but this week he is working later.

2. They don't go to the cinema very often, but when they go, they prefer comedies.

3. These two sisters have already spoken four foreign languages. Now they are learning a fifth.

4. He usually gets up about seven o'clock, but this month he is on holiday and so he is getting up later.

5. My dog usually barks at the postman — but look at that! For once, he is being friendly to the poor man.

6. They left for England this morning. I wonder whether they are travelling by air or by train.

7. I usually write my letters on Sunday, but I am writing this week's letters today because this coming Sunday we are going out.

8. I want to speak to the maids at once, please. Do you know where they are?
   — Yes, Mary is preparing dinner, and I think that Helen is setting the table in the dining-room.

9. The house smells unpleasant because we are having it repainted.

10. She is having her birthday party tomorrow and she is looking forward to it very much.

11. Children always look forward to their birthdays.

12. He is walking very slowly because the bottle which he is carrying holds nitroglycerine, and nitroglycerine explodes if it is shaken.

13. I see that you are becoming impatient with me, but I am trying my best to do it properly.

14. I am smoking a lot these days because I am studying for my final exams.

15. I do not like garlic when I smell it, but I love it when I taste it.

Здесь Present Simple используется для привычек, постоянных фактов и общих правил: usually leaves, prefer, explodes. Present Continuous нужен для временных действий, происходящих сейчас или в текущий период: is working this week, are learning, am studying. Present Perfect в третьем предложении показывает уже достигнутый результат к настоящему моменту: have already spoken.