10. John apologized (for, before, to) us (at, from, for) his words. 11. ... you (be told) already when your relatives (come) next week? 12. She has asked the clerk if all the trains (arrive) (on, in, at) time here. 13. I (not, feel) like visiting my relatives this year, so I (not, go). 14. It was announced that a new office block (construct) then. 15. Did you know that you (were to, had, must) prepare a report for the conference? 16. I couldn't pay for ... meal as I had left ... wallet at ... home, (a, an, the,-) 17. At the exhibition you will see (all, something, anything) you haven't met in your life yet. 18. "(At, on, in) accordance (with, to, from) the wishes of my people", the director said, "I am retiring from the company". 19. My son has ... very good German teacher, who knows ... language perfectly, (a, an, the, -) 20. My point of view is similar (with, to, and) yours, but different (out, with, from) Jenny's.

1) I am not waking up now.
Explanation: The present continuous tense is used to talk about actions happening at the moment of speaking. In this sentence, the action of waking up is happening now, but I am not doing it.

Step-by-step solution:
- Identify the verb: wake up
- Add the appropriate form of the verb "to be" (am) before the main verb: am + not + waking up

2) His father is watching TV now.
Explanation: The present continuous tense is used to talk about actions happening at the moment of speaking. In this sentence, the action of watching TV is happening now, and his father is doing it.

Step-by-step solution:
- Identify the verb: watch
- Add the appropriate form of the verb "to be" (is) before the main verb: is + watching

3) Morris is not going to school at the moment.
Explanation: The present continuous tense is used to talk about actions happening at the moment of speaking. In this sentence, the action of going to school is happening now, but Morris is not doing it.

Step-by-step solution:
- Identify the verb: go
- Add the appropriate form of the verb "to be" (is) before the main verb: is + not + going

4) Our parents are having breakfast right now.
Explanation: The present continuous tense is used to talk about actions happening at the moment of speaking. In this sentence, the action of having breakfast is happening now, and our parents are doing it.

Step-by-step solution:
- Identify the verb: have
- Add the appropriate form of the verb "to be" (are) before the main verb: are + having

Present perfect tense:
1) Bill has bought a new car this week.
Explanation: The present perfect tense is used to talk about past actions that have a connection to the present. In this sentence, the action of buying a new car happened in the past (this week), and it has a connection to the present (the car is still with Bill).

Step-by-step solution:
- Identify the verb: buy
- Use the appropriate form of the verb "to have" (has) before the past participle of the main verb: has + bought

2) Helen has cut her hair today.
Explanation: The present perfect tense is used to talk about past actions that have a connection to the present. In this sentence, the action of cutting her hair happened in the past (today), and it has a connection to the present (her hair is currently cut).

Step-by-step solution:
- Identify the verb: cut
- Use the appropriate form of the verb "to have" (has) before the past participle of the main verb: has + cut

3) They have just talked about it.
Explanation: The present perfect tense is used to talk about past actions that have a connection to the present. In this sentence, the action of talking happened in the past (just), and it has a connection to the present (the conversation is still relevant).

Step-by-step solution:
- Identify the verb: talk
- Use the appropriate form of the verb "to have" (have) before the past participle of the main verb: have + talked

4) Mario has never been to Moscow.
Explanation: The present perfect tense is used to talk about past actions that have a connection to the present. In this sentence, the action of going to Moscow (or the lack thereof) happened in the past, and it has a connection to the present (Mario has not been to Moscow up until now).

Step-by-step solution:
- Identify the verb: be
- Use the appropriate form of the verb "to have" (has) before the past participle of the main verb: has + never + been

1. I swam in the river last Sunday.

Explanation: To change the present tense sentence into the past tense, we need to change the verb "swim" to its past tense form, which is "swam". We also add the time phrase "last Sunday" to specify when the action took place.

2. I traveled to France last year.

Explanation: To change the present tense sentence into the past tense, we need to change the verb "travel" to its past tense form, which is "traveled". We also add the time phrase "last year" to specify when the action took place.

3. He was working in the garden the whole evening.

Explanation: To change the present tense sentence into the past tense, we need to change the verb "is working" to its past tense form, which is "was working". We also add the time phrase "the whole evening" to specify when the action took place.