Please choose the correct ending to complete the given sentence: Travel: [header] How to make red velvet brownies [title] Preheat the oven. [step] To ensure that the oven is hot enough to bake the brownies, you must preheat it. Set the temperature to 350 degrees fahrenheit (177 degrees celsius), and allow it to heat fully.

Ending1: [substeps] You can skip this step if you don't have a thermometer. Oven racks tend to be higher up around the edges. Ending2: Be aware that most recipes and ovens allow the oven to preheat for several minutes in order to impart a cool, distinct flavor that will make the brownies delicious. [substeps] Consider making the brownies for a victorian or batman-themed recipe. Ending3: You can use a thermometer or other heating device to ensure that it is safe to bake in the oven. [substeps] Make sure that the oven door and glass door are properly sealed. Ending4: [substeps] Keep an eye on your oven so you're aware when it reaches the proper temperature. Most models will beep or flash an indicator light to let you know.

Answer format: ending1/ending2/ending3/ending4