Hi!
The answer would have to be B, small, colored tiles.
To find out the correct answer you first need to know the definition of mosaic. A mosaic is defined as a picture or pattern produced by arranging together small colored pieces of hard material, such as stone, tile, or glass. From it's defintion we can see that mosaics are only made of tile, stone or glass, ruling out all the posibilities given except B. Therefore, color tiles is the answer (b).