Which of the following labels a stimulus within the environment?

The correct answer is "tact." A tact is a verbal behavior that involves labeling or naming objects, actions, or events in the environment. When an individual identifies or describes a stimulus, such as saying "dog" when they see a dog, they are engaging in tacting. This form of communication provides important information about the surroundings and helps foster social interactions and cognitive development.

In the context of behavior analysis, tacts are significant because they are one of the foundational forms of language that initiates communication based on what a person sees, hears, or experiences. This differs from echoics, which involve repeating what someone else has said, and mands, which are requests for something that the speaker wants or needs. Intraverbals refer to responses that aren't prompted by visual stimuli, often relating to conversations or answering questions, but they do not involve direct labeling of an item in the environment. Understanding tacts is essential for supporting individuals with autism in their communication skills and interactions.