Помогите, нужно выбрать только те предложение которые у Past Continuous​

Объяснение:

They were waiting for her when she finally arrived.

She was wearing a beautiful dress.

I was reading an Economist, while my sister was watching BBC.

He burnt his hand when he was cooking.

When I arrived, the lecture had already started and the professor was writing on the overhead projector.

I was writting a letter when the lights went out.

He suddenly realized that he was travelling in the wrong direction.

What were you doing?