- Dead organisms are the source of nutrients for decomposers
- Dead organisms rot
- Therefore, rotting organisms are a source of nutrients for decomposers

- A mushroom is a kind of fungus
- In the food chain process fungi have the role of decomposer
- Therefore, in the food chain process mushrooms have the role of decomposer

- Rotting organisms are a source of nutrients for decomposers
- In the food chain process mushrooms have the role of decomposer
- Hence, rotting organisms are a source of food for mushrooms

Hence, rotting organisms are a source of food for mushrooms
Question
What is a source of food and growth for a mushroom?

Context
- Dead organisms are the source of nutrients for decomposers 
- Dead organisms rot 
- A mushroom is a kind of fungus 
- In the food chain process fungi have the role of decomposer