умоляю!
4. We (met / were meeting) them when we (stood / were standing) at the bus stop.
5. I (slept I was sleeping) when his mother (came / was coming) back.
6. On Monday Mary (cooked / was cooking) lunch when the postman (brought/ was bringing) her a letter from her friend.
7. When the teacher (came / was coming) into the classroom, the children (sat / were sitting) at their desks.

Part 5
I (met/was meeting) a friend while I (did/was doing) the shopping. While I (paid/was paying) for my things, I (heard/was hearing) someone call my name. I (turned/was turning) round and (saw/seeing) Paula. She (wore/was wearing) bright red coat. We (decided/were deciding) to have a cup of coffee. While we (had/ were having) a drink, a waiter (dropped/was dropping) pile of plates. We all (got/were getting) a terrible shock. While the waiter (picked/was picking) up the broken plates, he (cut/was cutting) his finger. We (left/were leaving) the cafe and (said/were saying) goodbye. I (finished/was finishing) my shopping and (went/was going) home.

4. We were meeting them when we were standing at the bus stop.
In this sentence, the action of meeting the people and the action of standing at the bus stop were happening at the same time in the past. We use the past continuous tense (were + verb-ing) to show that both actions were in progress simultaneously.

5. I was sleeping when his mother came back.
In this sentence, the action of sleeping was happening in the past and it was interrupted by the action of his mother coming back. We use the past continuous tense for the sleeping action and the simple past tense for the action of his mother coming back.

6. On Monday Mary was cooking lunch when the postman brought her a letter from her friend.
In this sentence, the action of cooking lunch was happening in the past and it was interrupted by the action of the postman bringing the letter. We use the past continuous tense for the cooking action and the simple past tense for the action of the postman bringing the letter.

7. When the teacher came into the classroom, the children were sitting at their desks.
In this sentence, the action of the teacher coming into the classroom and the action of the children sitting at their desks were happening at the same time in the past. We use the simple past tense for the action of the teacher coming into the classroom and the past continuous tense for the children sitting at their desks.

Part 5:
I met a friend while I was doing the shopping.
In this sentence, the action of meeting the friend and the action of doing the shopping were happening at the same time in the past. We use the past continuous tense for the shopping action to show that it was in progress when the meeting happened.

While I was paying for my things, I heard someone call my name.
In this sentence, the action of paying for the things was happening in the past and it was interrupted by the action of hearing someone call my name. We use the past continuous tense for the paying action and the simple past tense for the action of hearing someone call my name.

I turned round and saw Paula. She was wearing a bright red coat.
In this sentence, the action of turning round and the action of seeing Paula were happening at the same time in the past. We use the past continuous tense for the turning action and the simple past tense for the action of seeing Paula.

We decided to have a cup of coffee.
In this sentence, the action of deciding to have a cup of coffee happened in the past. We use the simple past tense for this action.

While we were having a drink, a waiter dropped a pile of plates.
In this sentence, the action of having a drink was happening in the past and it was interrupted by the action of the waiter dropping the plates. We use the past continuous tense for the having action and the simple past tense for the action of the waiter dropping the plates.

We all got a terrible shock.
In this sentence, the action of getting a shock happened in the past. We use the simple past tense for this action.

While the waiter was picking up the broken plates, he cut his finger.
In this sentence, the action of picking up the broken plates was happening in the past and it was interrupted by the action of cutting his finger. We use the past continuous tense for the picking up action and the simple past tense for the action of cutting his finger.

We left the cafe and said goodbye.
In this sentence, the actions of leaving the cafe and saying goodbye happened in the past. We use the simple past tense for these actions.

I finished my shopping and went home.
In this sentence, the actions of finishing the shopping and going home happened in the past. We use the simple past tense for these actions.