Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to prepare benzocaine (fischer esterification ) [title] Add a magnetic stir bar , 1.0 g of p-aminobenzoic acid, and 10ml of absolute ethanol to a round bottom flask. [title] Swirl the mixture until the solid is completely dissolved. [title] Add 1ml of concentrated sulfuric acid drop wise with a pasteur pipette to the ethanol-aminobenzoic solution.

Ending1: [title] Sprinkle half of the mixture over the foam mixing surface. [title] Scrape any loose bits of foam leaving white slime behind, then pour in the rest of the solution into the abstained area. Ending2: [title] Assemble the pipettes, have the lid flat, and shake thoroughly on a flat surface. [title] Float half of the jar in the suspended mixture. Ending3: [title] Pour the solution into the containing flask. [step] The hermus pipette is included with the container. Ending4: [step] A solid will precipitate out of the solution. Remember, sulfuric acid is very corrosive and can cause serious chemical burns if allowed to come into contact with your skin.

Answer format: ending1/ending2/ending3/ending4