Which of the following rights cannot be assigned?

The reason a right that a statute expressly prohibits from being assigned is the correct answer lies in the principle of statutory law, which takes precedence in governing the assignability of rights. Certain rights or interests may be inherently linked to the specific obligations and responsibilities that a statute establishes, and as such, the law may dictate that these rights cannot be transferred to another party. For instance, rights related to personal services or specific entitlements, like certain government benefits, are typically non-assignable to ensure they remain closely tied to the individual or entity entitled to them.

In contrast, the other options describe situations that do not fall under explicit legal restrictions. For example, a right with no identifiable owner may simply lead to issues of enforceability or recognition rather than an outright prohibition on assignment. Similarly, a beneficial right under a contract tends to be assignable unless the contract itself restricts assignment, and a mere theoretical right does not imply a legal prohibition—it may just be impractical to enforce. Therefore, the uniqueness of statutory prohibitions places the first choice as the strongest answer.