Read this description of the life cycle of a mushroom.

1. A mushroom begins to grow underground as a single-celled "spore."

2. The spore grows into multicellular structures called "hyphae."

3. The hyphae absorb nutrition and detect when conditions are right to sprout a mushroom above ground.

4. The sprouted mushroom then forms new spores that can enter the ground and begin the life cycle again.

Which sentence about this life cycle shows that mushrooms need energy and respond to stimuli?