简答题The location of the tonic syllable (nucleus) is of considerable linguistic importance. The most common position of this is on the first lexical word of the tone-unit.简答题A low pre-head is the most common type. It’s produced at a comfortable pitch, somewhere below the middle of the speaker’s pitch range.简答题For a falling head, the pitch starts low and gradually falls throughout the head.简答题Among the four components of a tone unit, tonic syllable (or nucleus) is obligatory while pre-head, head and tail can be absent.简答题Tone languages are those languages in which the tones or pitch differences do not change the lexical meaning of a word or morpheme, but contain attitudinal or discoursal meanings.简答题There are different ways to divide sentences into tone units. For example, "There’s cheese salad and apple pie" can be divided into four tone units as in "There's cheese | salad | and apple | pie."