Rewrite the following sentences, using the words given.
4. My sister began to tát study English a year ago.
-> She has .....................................................................................................
6. Scientists began to tát fight against AIDS in 1980.
-> Scientists have ..........................................................................................
7. This hospital began to tát 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 đôi mươi years.
-> The Browns began ....................................................................................
16. When did she begin to tát tự research on lung cancer?
-> How long ...................................................................................................