Final answer:
The main theme of the poem "The Bluebell" by Emily Brontë is c) The impact of changes in nature on people.
Step-by-step explanation:
The main theme of the poem "The Bluebell" by Emily Brontë is c) The impact of changes in nature on people. The poem explores the idea that changes in nature can have a profound effect on human emotions and experiences. Brontë uses vivid imagery and sensory language to describe the beauty and power of the bluebell flowers, symbolizing the transformative and inspiring nature of the natural world.