Answer:
D). The swans in Yeats's "The Wild Swans at Coole" symbolize the speaker's youth.
Step-by-step explanation:
Narrowing a topic is vital to research for preparing as a response to literature. It includes the narrowing down of a wider topic in order to specify the area of research and emphasize the entire focus towards that particular area. The option that is sufficiently narrowed is option D and i.e. 'The swans in Yeats's "The Wild Swans at Coole" symbolize the speaker's youth' as it would help focus on a specific area. The other options are proposing either too wide topics that could be unmanageable or too short to be explained. Thus, option D is the correct answer.