Final answer:
Curley's wife feels apprehensive because talking to the ranch workers without Curley could lead to misunderstandings or confrontations due to Curley's jealous and aggressive nature.
Step-by-step explanation:
In John Steinbeck's novel Of Mice & Men, Curley's wife feels "suddenly apprehensive" when she realizes that Curley has gone into the house because she is worried about the consequences of being found talking to the men, especially George and Lennie, without her husband's knowledge. Curley is known for his jealousy and aggressive behavior, and the presence of his wife with the ranch workers could lead to misunderstandings or violent confrontations. Her apprehension is a reflection of her vulnerable position on the ranch and the strict social expectations placed upon her as Curley's wife, which demand that she avoids interaction with the workers without her husband present.