Please choose the correct ending to complete the given sentence: Home and Garden: [header] How to lay tile on concrete [title] Clean the surface of the concrete with a vacuum. [step] Follow up with a detergent, like tri-sodium phosphate (tsp). Make sure the area is well ventilated when you use this strong chemical cleaner.

Ending1: [title] Prepare the tile under the pressure of the vacuum. [step] Take notice of if any of the tile is loose under pressure. Ending2: [title] Check the levels on the floor to determine if the concrete is level. [step] If it is not level, you will want to purchase self-leveling underlayment to create an even surface. Ending3: [substeps] Do not use powder-based cleaners, as they can create strong fumes. [title] Mix the concrete together in a wheelbarrow or a spray bottle. Ending4: Clean very firmly so as not to dislodge plaster or grit. [title] Sand the surface of the concrete completely with a 600 grit sandpaper.

Answer format: ending1/ending2/ending3/ending4