Select from options: Continue writing the next sentence.

How to make gratin dauphinoise without cream
Preheat the oven.
To ensure that the oven is hot enough to bake the gratin, you must preheat it. Set the temperature to 425 f (220 c), and allow it to fully heat.

Choices:
(a). The oven should be preheated when you plan to bake the gratin. If the oven has not been preheated yet, just turn it on and let it preheat.;
(b). If you've programmed your oven, it should come with an oven thermometer. Make sure it's set to 420 f (220 c) before you start cooking the gratin.;
(c). Make sure that there are no vents, as the temperature rises in your oven. Smear the butter and the flour over the surface of the gratin.;
(d). Rub the garlic clove over a shallow baking dish. For the gratin, you'll need a fairly shallow baking dish.;
Answer:
(d).