It is either C or D. The poem did say stifling....
A SATURATED meadow,
Sun-shaped and jewel-small,
A circle scarcely wider
Than the trees around were tall;
Where winds were quite excluded,
And the air was stifling sweet
With the breath of many flowers,—
A temple of the heat.
It sounds very suffocating as you read the poem so I would go with D. but I would also like you to look into C. more because it says the intense smell of the flowers.
Hoped I helped!