The correct answer is D. Field.
A field is a control that is used to store data. It is typically associated with a text control, which is used to enter data into the field. When you select a field, its associated text control is also selected and the two controls will act as one when manipulated.
A text control is a control that is used to enter text. It is typically used to enter data into a field.
A form is a container for controls. It is typically used to group controls together and to provide a way to interact with the controls.
A label is a control that is used to provide information about another control. It is typically used to identify the control or to provide instructions on how to use the control.