When Mr. Ruan saw him, he was using his cell phone. When/ While other students were reading, he was using his cell phone. I found one student using his cell phone when I took the photo.

1. __________ he was born in Austria, his father was a peasant at that time. 2. __________ he was very young, Mozart had a lot of musical talent. 3. __________ he was still a teenager, he was a big star.

When

When

When

/While

/While

Conclusion: when和while引导的从句强调“在…过程中”，表示时间 段，谓语动词通常为延续性动词或表状态的be动词。when还可表示时间点，谓语动词可以是非延续性动词。