I (take) the lift / all the lights (go) out. WHEN
I was taking the lift when all the lights went out.
My mother (help) the driver / we (wait) for the ambulance. WHILE
My mother helped the driver while we were waiting for the ambulance.
Your grandma (arrive) / you (watch) TV. WHILE
Your grandma arrived while you were watching TV.
We (study) in the library / we (hear) the fire alarm. WHEN
We were studying in the library when we heard the fire alarm.
We (hear) a crash / we (have) a music lesson. WHILE
We heard a crash while we were having a music lesson.
I (walk) into the bank / the men (rob) it. WHILE
I walked into the bank while the men were robbing it.