Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to check the freshness of baking powder [title] Boil some tap water. [step] Use tap water and fill a kettle to the minimum fill line. You only need ½ cup (118 ml) of hot water to test the baking powder, but filling the kettle to the minimum fill line will ensure the heating element doesn't overheat.

Ending1: Turn on the kettle and bring the water to a boil. [substeps] Don't use more water than you need, otherwise the kettle will waste energy heating the extra water. Ending2: Make sure you have warm, but not boiling, water. [title] Place a baking sheet under the oven vent (the bottom of the oven). Ending3: This is also a good time to test the moisture content of the water in a fresh batch. [substeps] Fill the kettle just a quarter full with water. Ending4: [title] Sprinkle the baking powder into the water. [step] Transfer the powdered glass directly into the boiling water.

Answer format: ending1/ending2/ending3/ending4