In this circuit, the load is the object that consumes electrical energy to perform work. In your case, the hot plate is the device that converts electrical energy into heat energy to boil water for tea. Therefore, the correct answer is:
D: the hot plate.
The tea kettle is not the load; instead, it is the container being heated by the load (hot plate). The battery provides the electrical energy, and the wires facilitate the connection between the components.