1. The teacher is checking his email while he is talking on the phone.

Yesterday evening, the teacher was checking his email while he was talking on the phone.

1. The cat is sitting on the printer.

When I opened the door this morning, the cat was sitting on the printer.

1. We are having a video conference when the webcam stops working.

Last week, we were having a video conference when the webcam stopped working.

1. As she is saving an email attachment, Paige clicks on a link.

Yesterday at lunchtime, Paige was saving an email attachment when she clicked on a link.

1. She started to work at the school canteen two months ago. (for)

She has been working at the school canteen for two months.

1. The English teacher started teaching at our school some years ago. (since 2009)

The English teacher has been teaching at our school since 2009.

1. When did she start learning English?

How long has she been learning English?

1. When did you first meet?

How long have you known each other?