Each TextField has a text property that's returned by its textProperty method as a StringProperty. The StringProperty method receives an ObservableValue as an argument. When the ObservableValue changes, the bound property is updated accordingly.

a. join
b. bind
c. attach
d. tie

B: Bind

Explanation:

JavaFX property binding permits the synchronization of the value of two properties in such a way that whenever there is a change in one of the properties, there is an immediate update on the value of the other property. In this way, The StringProperty method bind receives an ObservableValue as an argument. When the ObservableValue changes, the bound property is updated accordingly.

you are welcome for my answer it is b⇔⇒⊕