Please choose the correct ending to complete the given sentence: Food and Entertaining: [header] How to make cheeseburger soup [title] Preheat the oven. [step] To toast the hamburger buns for the crouton topping, the oven must be hot enough. Set the temperature to 400 degrees fahrenheit (200 degrees celsius), and allow it to fully preheat.

Ending1: The easiest way to tell when it is hot enough is to check the thermometer. [substeps] If the thermometer reads between 1600º f (3 degrees celsius) and 315 ° f (121 ° c) then it is hot enough. Ending2: Bake them for approximately 30 to 45 minutes, or until the buns are golden brown and the consistency of peanut butter. [substeps] Check the temperature of the buns every 30 to 60 minutes while they're in the oven. Ending3: [substeps] If the oven is not preheated, it will be more difficult to make your sandwich chicken. If you cannot warm the chicken in the oven for an hour or more, you can call a friend to lend you their oven. Ending4: [substeps] If you prefer, you can toast the buns in a toaster oven rather than a standard oven. [title] Spread the bun pieces out on a baking sheet.

Answer format: ending1/ending2/ending3/ending4