Answer:
Serious.
Explanation:
'We Real Cool' is a poem extended in eight lines, written by Gwendolyn Brooks. The poem is about a group of rebellious teenage boys, who meets an unfortunate fate.
The language in the last line of the poem creates a serious tone. The boys have met their unfortunate fate for their rebellion, they died. Thus this invocation of death for rebellion creates a serious tone. The poem suggests that rebellion has have serious consequences to pay.
Therefore, the correct answer is option (D), tone.
