1)chuyển thành câu bi động

he had decorated the house before last Tet

---> The home had been decorated before last Tet.

we have our mother wash the clothes

---> Our clothes have been washed by our mother.

2) chuyển đổi giữa if và unless

we won't go on holiday unless we have enough money

----> If we don't have enough money, we won't go on holiday.

she can't apply for the job if she doesn't know French

----> Unless she knows French, she can't apply for the job.