Under which condition would Ted be eligible for survivor benefits after Bill's death?

Ted would be eligible for survivor benefits after Bill's death if they lived in a state recognizing common law marriage. Common law marriage is a legal framework in certain jurisdictions that recognizes a relationship as a marriage even if no formal marriage ceremony or certificate has taken place, provided the couple meets specific criteria such as living together for a significant period and intending to be married.

In the context of survivor benefits, this legal recognition means that Ted could claim benefits as a surviving spouse because the law would consider their relationship equivalent to a legally married couple, thus making him eligible for the benefits that typically go to a spouse upon the death of the partner.

This distinguishes the correct answer from the other options, which do not provide sufficient grounds for eligibility on their own. For example, simply having a marriage certificate is not relevant since it does not address the situation of mutual recognition of their relationship under common law. Similarly, filing for joint benefits is not a requirement for survivor benefits and income levels are not a determining factor in the context of spousal eligibility for these benefits.