Final answer:
In a personal auto policy, a trailer would typically be covered, while motorcycles, mobile homes, and tractor-trailers would require specialized policies due to their unique nature and use.
Step-by-step explanation:
The question asks which of these would be a covered auto under a personal auto policy: 1) motorcycle 2) trailer 3) mobile home 4) tractor-trailer. Typically, under most standard personal auto policies, a trailer designed for use with a private passenger auto is considered a covered auto. This typically extends to trailers such as those used for moving personal possessions or for personal recreational purposes. Motorcycles, mobile homes, and tractor-trailers usually require specialized policies. Motorcycles are generally not considered private passenger autos and thus need specific motorcycle insurance. Mobile homes are dwelling units and also require their own form of insurance. Tractor-trailers are commercial vehicles and are covered under commercial auto policies, not personal auto policies. Therefore, among the listed options, a trailer would typically be included as a covered auto under a personal auto policy.