This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to install marble floor tile
Wear gloves, eye protection and a facemask.
These will protect your hands, eyes and lungs as you install your marble tiles.
Remove any existing tiles.

Pick from:
[+] They should not be stuck to your dress shirt, dress pants, etc. This will mess up your tile tile pattern, if they were to fall down while you were still wearing your clothes, you are sure to get them lodged on your dress pants.;
[+] If there are any tiles currently mounted on the ceiling, do so before removing them. If you're removing tiles that are cost-prohibitive, wear safety gear when using a tile removal tool.;
[+] Take off any tile that might have fallen off during the installation. If you purchased the tile from a home improvement store, , the paint is likely to flake over time.;
[+] If you are installing the marble on a floor that is already tiled then you must remove the old tiles first. Ceramic tiles can be smashed with a hammer and then removed.;
The answer is:
If you are installing the marble on a floor that is already tiled then you must remove the old tiles first. Ceramic tiles can be smashed with a hammer and then removed.