Answer: Write down a short story with a determinate amount of "complex" words? Challengue accepted.
Step-by-step explanation:
The first thing here is that the words we´re trying to use, some are basic, some are not. So don´t worry if you have a couple of structure mistakes.
Second step is that we need to define the concept "story". If we´re looking for something like a tale, then you can start writing about someone (even an animal) who´s having personal or social issues such as discrimination, frustration or lack of life vision. A topic like that can fulfil your 3 paragraphs task.
Third step can be considered as an observation.
If the story you´re looking for has to be more complex, then the sky is the limit. Almost every nowadays situation include the words on your notebook.