Beyond tone, a poet's attitude toward his or her subject reveals to us a poem's
a. theme.
b. structure.
c. diction.
d. subject?

A is the correct answer. The poet’s attitude toward their subject reveals the theme of the poem; for example, if it is a poem about war but they are talking about it with a negative attitude, the theme of the poem is likely to be anti-war, pacifism or anti-imperialism.