Answer:
A. ObservableList
Step-by-step explanation:
ObservableList is a type of list that enables users to track changes when they occur. When ObservableList are bind to the ListView, it notifies the observer automatically to any changes made. It is a type of interface found in the javaFx collections. When applying ObservableList, a standard list is first created which then wrapped with an ObservableList. Then when changes are made, the ListChangeListener is automatically notified.