Final answer:
A bridge can potentially be covered under a commercial inland marine policy. Charging an actuarially fair premium to the whole group instead of to each separately can lead to adverse selection and destabilize the insurance pool.
Step-by-step explanation:
In reference to a commercial inland marine policy, which can cover unique or mobile items, the correct choice from the options provided is a bridge. This type of policy is designed to cover property that is movable or involved in transportation or communication, making a bridge a potential item that could be covered due to its significance in transportation infrastructure.
Regarding the part of the question about insurance premiums, when an insurance company charges an actuarially fair premium to the group as a whole rather than to each group separately, this can lead to a situation where members of lower-risk groups may feel that they are paying unfairly high premiums as they are not causing as much loss as the higher-risk group members. This could result in adverse selection, where those good risks choose to leave the pool, leaving behind a group with a higher average risk and therefore higher expected losses, which could eventually make the insurance pool unsustainable.