Such movement is more economical, and the mysteries of this argument-adjunct asymmetry will be revealed, as shown in 7and 8 Zhangsan like someone but I not know be who ' Z h a n g s a n l i k e s someone, but I don ' t k n o w wh o ' shi exists before the wh-argument Shei ' Wh o ' is that the trace of this wh-argument cannot be antecedent-governed by its antecedent in the lower hierarchical level, and thus must be lexically-governed or head-governed by a lexical head, such as the preceding verb Zhidao ' k n o w . '
there exists a barrier (Chomsky 1986) between this lexical head and the covert wh-argument trace, which has blocked the verb from governing into the intervening CPs.