imagine that you are conducting tests shortly after a nuclear accident. Using potted moss plants as you experimental organisms, design a experiment to test the hypothesis that the frequency of mutations decreases with the organisms distance from the source of radiation

Take two potted plants and provide equal conditions to both.

Explanation:

Two potted plants i.e. one is placed near the nuclear accident site while on the other hand, the other is placed far away from the nuclear accident. Provide equal conditions to both plants so that we can find out the hypothesis that  the frequency of mutations decreases with the organisms distance from the source of radiation. The result shows that the potted plant that is located near to the nuclear accident site having high frequency of mutation as compared to other plant due to the radiation present at that location.

not sure if this what   you'r looking for would be percent composition