1. They have talked/have been talking about it all morning. 2. He's not here because he has been going/has gone to work. He'll be back at 4 o'clock. 3. The children cleaned/have been cleaning the playground yesterday. 4. She has studled/has been studying all day. 5. I worked/have benn working without a break since 8 o'clock 6. I have been walking/walked to the park last week.
С объяснением срочно!!

Спасибо)

1. Talked.2. Going.3. Have.4.Studied5. Have.6 Walked.Объяснение: в 1 уже есть глагол have. Во 2 уже есть частица has. В 3 уже есть глагол cleaning. В 4 уже есть частица has. В 5 уже есть глагол working. В 6 прошедшее время, нужен глагол с ed окончанием, т.е. Walked. Не за что)