adverbial -predicate existential sentence的用法和样例：
- Existential sentence is concluded from the perspective of function, and belongs to sentence category.
- A sentence indicating the existence, appearance or disappearance of a person or an object is called an existential sentence.
- The existential sentence sometimes is chosen to meet the connection of text, sometimes the need of the psychological view of point.
- Existential sentence and subject-predicate sentence differ mainly in their pragmatic values, each having different information focuses.