Please choose the correct ending to complete the given sentence: Food and Entertaining: [header] How to make gratin dauphinoise without cream [title] Preheat the oven. [step] 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.

Ending1: [substeps] 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. Ending2: [substeps] 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. Ending3: [substeps] Make sure that there are no vents, as the temperature rises in your oven. [title] Smear the butter and the flour over the surface of the gratin. Ending4: [title] Rub the garlic clove over a shallow baking dish. [step] For the gratin, you'll need a fairly shallow baking dish.

Answer format: ending1/ending2/ending3/ending4