Final answer:
The part of the rising action that adds the most suspense is when Rainsford hears the dogs barking in the distance.
Step-by-step explanation:
The part of the rising action that adds the most to the story's suspense is when Rainsford hears the dogs barking in the distance. This moment increases the tension and foreshadows the danger Rainsford is facing. It creates anticipation and suspense as the reader wonders what lurks in the darkness and what will happen to Rainsford.