Which part of a circuit creates an electric force field that makes it possible for the circuit to work?

bulb

buzzer

motor

voltage source

Here, Your answer would be option D) Voltage Source.

Charge flows from it in a particular direction, and a charge ( static or dynamic ) creates an electric field around it (can be experimentally observed by a test charge), whereas all the other options are appliances which needs current ( rate of flow of charge ) to work. 

In short, Your correct Answer would be Option D)-Voltage Source.

Hope this helps!