Final answer:
The speaker's tone in the poem is best described as regretful, as the personified grass reflects sorrowfully on the historical events it covers. So the correct answer is Option B.
Step-by-step explanation:
The question asks for the best description of the speaker's tone in a poem that references Ypres, Gettysburg, and other major battles, and where the grass is seemingly personified, speaking lines such as "cover all". Option B, suggesting that the grass is regretful about hiding the aftermath of terrible historical events like the battles listed, best captures the tone of the poem. This implies a sense of sorrow and reflection on the part of the grass, which covers the scars of war, contrasting with the other options that suggest pride, indifference, or a sense of vindication in sacrifice.