1. She has already been to all the capital cities of Europe.
2. John traveled around Europe last year.
3. Have you ever lived in a foreign country?
4. My friend knows a lot because he reads a lot.
5. She went home two days ago.
6. David started school in 1990.
7. I left home early last night.
8. Is she still watching this program? - No, she has just watched it.
9. We did not see them last week.
10. It stopped snowing an hour ago.
11. When did you arrive in Paris?
12. We did not know about the disco last night.
13. Have you read this book?

This exercise is about using the correct tense of verbs in English. Let's go through each sentence carefully to fill in the blanks with the correct forms of the verbs.

She has already been to all the capital cities of Europe.
- Here, we use the present perfect tense (has been) because it refers to life experiences at an indefinite time in the past.
John traveled around Europe last year.
- The simple past tense (traveled) is correct because it refers to a completed action in the past, specified by 'last year'.
Have you ever lived in a foreign country?
- The present perfect tense (have lived) is used here for asking about life experiences up to now.
My friend knows a lot because he has read a lot.
- Present perfect tense (has read) is used to show that the reading has occurred over time and its influence continues.
She went home two days ago.
- Simple past tense (went) is correct for actions that happened in the past and have a specific time marker (two days ago).
David started school in 1990.
- Use the simple past tense (started) because it refers to an action completed in the past, indicated by a specific time.
I left home early last night.
- Simple past tense (left) is used for a completed action with a time reference (last night).
Is she still watching this programme? - No, she has just watched it.
- Present perfect tense (has just watched) indicates a recently completed action.
We did not see them last week.
- The simple past (did not see) is used for a completed action with a time reference (last week).
It stopped snowing an hour ago.
- Simple past tense (stopped) is used as it is a completed action with a specific time reference (an hour ago).
When did you arrive in Paris?
- Simple past tense (did arrive) is needed for questions about specific events in the past.
We did not know about the disco last night.
- Simple past tense (did not know) is used here for referring to lack of knowledge at a specific past time (last night).
Have you read this book?
- Present perfect tense (have read) asks about the experience of reading this book at an indefinite time in the past.

In summary, this exercise focuses on applying the correct English verb tenses based on the context of time and the meaning intended in each sentence. By identifying the hints provided by time phrases and question words, decisions on whether to use past, present perfect, or past perfect tenses become clearer.