I believe the correct answer is B. The modifier "wearing a blue dress" is placed far from the noun which is supposed to modify - Stacey. Such as it is, it could easily be attributed to another noun, the stage. It would seem that the stage was wearing a blue dress, rather than Stacey. This is easily fixable with a comma between "stage" and "wearing".
The C and D sentences are also a little bit awkward, but they don't contain a misplaced modifier.
Answer:
The letter that is supposed to be delivered to Romero, hasn't been delivered because of the infection. So Romeo will not know the plan.
Explanation:
The rising action is the part of the plot in which conflict gradually builds in intensity.