The correct answer is C because Managed Instance Groups offer an AutoHealing feature. This feature conducts health checks and automatically recreates instances if the application is unresponsive. This ensures high availability by proactively maintaining instances in a RUNNING state. AutoHealing is particularly effective for detecting and rectifying application-specific issues like freezing, crashing, or overloading, beyond just checking the instance state. Options A and D are incorrect as these features do not exist. Option B is incorrect because auto-updating is designed for deploying new software versions to instances, not for ensuring application responsiveness or availability.