Rewrite the following sentences, using the words given. 4. My sister began to study English a year ago. -> She has ..................................................................................................... 6. Scientists began to fight against AIDS in 1980. -> Scientists have .......................................................................................... 7. This hospital began to use laser treatment 5 years ago. -> This hospital has been  ............................................................................. 8. She started working as a book keeper for this company 5 years ago. -> She has ..................................................................................................... 10. How long have you studied English? -> When ......................................................................................................... 11. The Browns have been living in London for 20 years. -> The Browns began .................................................................................... 16. When did she begin to do research on lung cancer? -> How long ...................................................................................................

4. My sister began to study English a year ago.

-> She has studied English for a year.

6. Scientists began to fight against AIDS in 1980.

-> Scientists have fought against AIDS since 1980.

7. This hospital began to use laser treatment 5 years ago.

-> This hospital has been  using laser treatment for 5 years.

8. She started working as a book keeper for this company 5 years ago.

-> She has been working as a book keeper for this company for 5 years.

10. How long have you studied English?

-> When did you start studying English?

11. The Browns have been living in London for 20 years.

-> The Browns began living in London 20 years ago.

16. When did she begin to do research on lung cancer?

-> How long has she done research on lung cancer?