Answer: Liability insurance.
Explanation:
In this situation, Stephen could potentially use his auto insurance to cover the accident. Specifically, he could rely on his liability insurance, which is a common type of coverage that helps pay for damages to other people's property or injuries caused by an accident that he is at fault for.
Liability insurance typically includes property damage coverage, which would help cover the cost of replacing Keisha's bumper. It's important to note that the availability and extent of coverage may depend on Stephen's specific auto insurance policy and any deductibles or limits that may apply.