The correct option is Stateful behavior. Function as a Service offerings are generally designed to be stateless and not to retain in memory state across separate invocations.

Serverless functions are usually short lived and ephemeral so they are started and stopped frequently and scaled out concurrently. Because of that functions rely on external systems such as databases caches or object storage to hold persistent data and to share state across invocations. Designing functions to be stateless makes scaling simple and prevents issues with consistency when many instances run at the same time.

Automatic scaling is not the correct choice because FaaS platforms commonly provide automatic scaling. Functions are typically scaled up and down in response to incoming requests or events without manual intervention.

Short lived execution times is not the correct choice because serverless functions are commonly expected to have short execution durations and many providers enforce or encourage time limits for function runs.

Event driven invocation is not the correct choice because FaaS is often triggered by events such as HTTP requests messages from queues or changes in storage and that event driven model is a core characteristic of serverless functions.

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