How to add a new choice field using WSS Object Model?

SPList list = site.Lists["Demo"];
StringCollection choices = new StringCollection();
choices.Add("AP");
choices.Add("MP");
choices.Add("HP");
list.Fields.Add("State", SPFieldType.Choice, false, false, choices);
SPFieldChoice fldChoice = (SPFieldChoice)list.Fields["State"];
fldChoice.EditFormat = SPChoiceFormatType.Dropdown;
fldChoice.Update();
list.Update();