1. I (know) Alex since he was a child, 2. We (play) tennis since 2 o'clock, 3. They (play) tennis three times this week, 4. These children (study) English for four years now, 5. He (study) his lesons already

1. I (know) Alex since he was a child
2. We (play) tennis since 2 o'clock
3. They (play) tennis three times this week
4. These children (study) English for four years now
5. He (study) his lesons already
6. Jane ( work) in this factory since she was eighteen
7. We ( wait) her for three months and she ( travel ) six countries so far