$1$. We were having breakfast when the mailman arrived.

$2$.While everyone were sleeping, Paul was watching TV.

$3$.I was dreaming about a long vacation when the alarm clock went off

$4$.While I was practicing the piano late last night, I heard a strange noise.

$5$.The sheep were gazing in the field when they were scared by the noise.

$6$.What did you do when the earthquake was happening yesterday?

$7$. I was running to catch the bus when I saw Jim.

$8$. When you met James last night, what was he wearing?

$9$. Some people were chatting while others were playing games at the party last night.

$10$ . It was raining at this time yesterday so we cancelled the barbecue.

1)We/ have/ breakfast/ when/ the mailman/ arrive.

⇒We were having breakfast when the mailman arrived.

2)While/ everyone/ sleep/ Paul/ watch/ TV.

⇒While everyone were sleeping, Paul was watching TV.

3) I/ dream/ about/ long/ vacation/ when/ the alarm clock/ go/ off.

⇒While I was practicing the piano late last night, I heard a strange noise.

4)While/ I/ practice/ the piano/ late/ last night,i/ hear/ strange/ noise.

⇒While I was practicing the piano late last night, I heard a strange noise.

5) The sheep/ graze/ in/ the/ filed/ when/ they/ be/ scared/ by/ the/ noise.

⇒The sheep were gazing in the field when they were scared by the noise.

6)What/ you/ do/ when/ the earthquake/ happen/ yesterday?

⇒What did you do when the earthquake was happening yesterday?

7)I/ run/ to/ catch/ the bus/ when/ I/ see/ Jim.

⇒I was running to catch the bus when I saw Jim.

8)When/ you/ meet/ James/ last night/ ,/ what/ he/ wear?

⇒When you met James last night, what was he wearing?

9)Some people/ chat/ while/ others/ play/ games/ at/ the party/ last/ night.

⇒Some people were chatting while others were playing games at the party last night.

10) It/ rain/ at this time/ yesterday/ so/ we/ cancel/ the barbecue

⇒It was raining at this time yesterday so we cancelled the barbecue.