[Solved] It has been suggested that the fraternal birth-order effect is a result of A) erotic plasticity. B) refractory periods. C) a maternal immune response. D) mass-media norms. Unearned Subscriptions: Income received in advance for subscriptions that have not yet been fulfilled or services that have not yet been provided. Liability Accounts: null Revenue Recognition Principle: An accounting principle that outlines the specific conditions under which revenue is recognized. Unearned Rent Revenue: Income received by a company for rent that has not yet been earned because the service period has not occurred.