Final answer:
The antagonist in Saki's story 'The Open Window' is the dog.
Step-by-step explanation:
In Saki's story "The Open Window," the antagonist is the dog. The dog's behavior causes confusion and chaos in the story, leading to misunderstandings and a tense situation. For example, the dog's sudden barking disrupts the conversation between the niece and the visitor, creating a sense of tension and unease.
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