Multi-choice problem: Continue writing the next sentence in this paragraph:

How to clean a travertine shower
Clean your shower after you use it.
The running water in your shower loosens surface dirt and softens soap residue on your travertine tiles. For optimal results, tackle shower cleaning after your shower has primed the tiles for you.

pick from the following.
[i] Use an enzyme-based soap in place of a regular soap if your tiles are water-resistant. Then use an enzyme-based soap rather than a regular soap or soapy soap, as these are less effective at scraping or killing germs and debris from tiles.
[ii] Run a ceramic or glass washer under hot, soapy water for an additional three to five minutes, just to ensure that you have enough water in your shower. Once all the water has been drained, dry the tile surface with a clean towel before proceeding with flushing it with hot water.
[iii] Spray your wet tiles with a non-acidic soap scum remover. Travertine, like all limestones, is extremely sensitive to acids.
[iv] Running cold water over your shower heads when they're dirty won't distribute any soap: and you could end up softening your built-up grime while showering. Try using a degreaser to clean your shower head, or use a degreaser specifically designed for travertine.
[iii]