Question

Your teacher has asked you to write a story called trapped

Answer 1

I cannot write the full story for you, but I can give some recommendations.

You can understand "trapped" metaphorically and you can describe a family that had to spend a lot of money on the medical treatment of their child and now they have to work hard to pay their debt. They cannot change a job since they would risk loosing their payment, and so they are "trapped" in their life.