Поставьте глаголы, стоящие в скобках, в зависимости от смысла, в Present Indefinite, Present Continuous, Present Perfect или Present Perfect Continuous:
1. Mary (to learn) French at the University. She (to learn) English since last autumn. 2. They are busy now. They (to discuss) an important question. They (to discuss) it since five o'clock. 3. Where is John? - He (to work) in the library. - He (to work) long? - Yes, he (to work) since morning. 4. My son (to be) in hospital. He (to be) there for ten days. 5. Mr. Ivanov (to teach) French. He is a very experienced teacher. He (to teach) French for fifteen years. 6. I (to know) Jack well. - Since when you (to know) him? - I (to know) him since 1970.