1/ They were playing chess when he went in

2/ While I was eating lunch, the cat jumped over

3/ The teacher came in to the class while we were playing cards

4/ The secretary was working when the boss phoned

5/ While the mechanic was repairing the car, the man called him

6/ When I was waiting for the bus, I met my old friend

7/ He was driving to work when the car broke down

8/ When thay are learning English, the lights went out

9/ When the vet was examining the dog, it was banking

Cho xin hay nhất ạ!

1.They\play\chess\when\he go in.

->They were playing chess when he went in.

2. While\I\eat\lunch\the cat\jump over.

->While I was eating lunch, the cat jumped over. 

3. The teacher\come\into the room\while\we\play\cards.

->The teacher came into the room while we were playing cards.

4. The secretary\work\when\the boss\phone.

->The secretary was working when the boss phoned.

5. While\the mechanic\repair\the car\the man\call him.

->While the mechanic was preparing the car, the man called him.

6. When\I\wait\for the bus, I\meet\my old friend.

->When I was waiting for the bus, I met my old friend.

7. He\drive\to work\when\the car\break\down.

-> He was driving to work when the car broke down.

8. When\they\learn\english,the lights\go\out.

->When they were learning English, the lights went out.

9. When\the vet\examine\the dog\it\bank

-> When the vet was examing the dog, it was banking?