按要求完成句子

1. I was three years old when I started doing the things.(对画线部分提问)

    _____ _____ _____ you when you started doing the things?

2. I went to the zoo last Sunday.(对画线部分提问)

    What _____ _____ _____ last Sunday?

3. I saw some sharks.(改为一般疑问句)

    _____ you _____ _____ sharks?

4. The students had a terrible school trip.(改为否定句)

  The students _____ _____ a terrible school trip.

苍蝇可以引起伤寒传播么？