In this case, `` is a na-adjective, and the situation is different from potential verbs, which optionally allow accusative case marker ``. In order to have a noun phrase marked as accusative case, there has to be a transitive verb. In the expression ``, there is no transitive verb that can assign accusative case, and so it is ungrammatical.
> ×
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However, if the relevant part is embedded as a subordinate clause of a transitive verb, then you can use ``. In the example below, `` has the ability to assign accusative case, and since it does not have its own direct object, and hence has not used up this ability, it can assign accusative case to the object `` of the subordinate clause.
> []
> []