Question

When a poet changes the meter in a poem, it forces the reader to

Answer 1

The correct answer should be D. emphasize key words

By changing the meter you change the accentuation pattern which automatically emphasizes some parts of the lines.

Answer 2

When a poet changes the meter in a poem, it forces the reader to emphasize key words. D is the correct option.

By changing the meter, there is a shift in the accentuation pattern which automatically emphasizes some parts of the lines.  

Meter creates a specific rhythm to a poem. When the meter changes, the reader will have to stops or slows down while reading  the poem which emphasizes any key words.