 In (25), the asterisk indicates intuitive deviance; in (25S), it indicates the hypothesized source of this deviance—viz., that the auxiliary verb cannot be displaced from the embedded relative clause. The ill-formedness of (25S) is striking, since one can sensibly ask whether or not the boy who was happy sang. One can also ask whether or not (26) is true. But (27) is not the yes/no question corresponding to (26).