sentences:  Null determiners and null complementizers are empty categories that are the result of more recent research.These null heads are positions which end up being unpronounced at the surface level but are not included in the anaphoric and pronominal features chart that accounts for other types of empty categories.Null determiners are used mainly when the Theta assignment of a verb only allows an option for a DP as a phrase category in the sentence (with no option for a D head).