The doctor (operate on) ... the patient when he (wake up).... .
was operating/woke up
The man (swim)... when the boy (fall)... to the pool.
was swimming/fell
I (play)... the piano when my father ( arrive).... .
was playing/arrived
The dog (bark).... when the postman (arrive).
was barking/arrived
The train (start)..... while the guard (blow)... the whistle.
started/ was blowing
We (listen)... to music when the lights (go off) ....
Were listening/went off
I (catch)... fireflies when it (start)... raining.
was catching/ started
Bradley Chalkers (read)....a book when some boys (push) him to the floor.
was reading/push.
My granny (sew) .... when her husband ( leave).... the house.
was sewing/left
The tigers (hunt) ...when a man (appear) .... and (shoot)... one of them.
were hunting/ appeared/shot
The wind (blow).... when the door (slam)... .
was blowing/slammed
My sister (drop) ...the milk while she (have) ....breakfast.
dropped/was having
Elsa (ice-skate).... when everything (freeze) ... around her.
was skating/froze
While the girl (cry).... the fairy (touch) her with her magic wand,
was crying/touched
While I (walk) .......... to school, I (stop) .......at a shop to buy some sweets.
was walking/ stopped
The sun (shine)... when suddenly it (start) ...to rain.
was shining/started
We (dance)... when a policeman (knock)... on the door.
were dancing/knocked
The princess (play)...ball when she (see)... an ugly frog.
was playing/saw
When my mom (open) .... the door, I (do)..... my homework.
opened/was doing
The parrot (fly).... when the man (catch) ...it.
was flying/caught