Final answer:
The main theme of the poem is the power of hope, and the quote that supports this theme is 'And sweetest in the gale is heard;'.
Step-by-step explanation:
The main theme or message in the poem 'Hope is the Thing with Feathers' by Emily Dickinson is the power of hope to sustain and uplift the human spirit, even in the face of adversity. The poem uses the metaphor of a bird with feathers to represent hope, emphasizing its lightness and resilience. The quote that best supports this theme is 'And sweetest in the gale is heard;' (A). This line suggests that hope is at its strongest and most comforting during difficult times.