Groenendijk and Stokhof (1984, 1996; Groenendijk 1999) provide a logically attractive theory of the semantics of natural language questions, commonly referred to as the partition theory. Two central notions in this theory are entailment between sentences and answerhood. For example, the question Who is going to the party? entails the question Is John going to the party?, and John is going to the party counts as an answer to both. Groenendijk and Stokhof define these two notions in terms of partitions of a set of possible worlds. We provide a syntactic characterization of entailment between questions and answerhood. We show that answers are, in some sense, exactly those formulas that are built up from instances of the question. The result lets us compare the partition theory with other approaches to interrogation