Viết lại câu sao cho nghĩa không đổi sử dụng từ gợi ý cho sẵn

Viết lại câu sao cho nghĩa không đổi sử dụng từ gợi ý cho sẵn.

1. David had gone home before we arrived. – After …………………………………………………………………………………….

2. We had lunch then we took a look around the shops. – Before ……………………………………………………………………………………

3. The light had gone out before we got out of the office. – When …………………………………………………………………………………….

4. After she had explained everything clearly, we started our work. – By the time …………………………………………………………………………….