Four food samples, W, X, Y and Z, were each tested as shown in the table below. Each sample contains only one or two of the following: glucose, sucrose, starch, protein and lipid.
| Test |
Sample W |
Sample X |
Sample Y |
Sample Z |
| Benedict’s test (heated) |
brick-red precipitate |
stays blue |
stays blue |
stays blue |
| Boiled with dilute HCl, neutralised, then Benedict’s test |
brick-red precipitate |
brick-red precipitate |
brick-red precipitate |
stays blue |
| Iodine solution |
yellow-brown |
yellow-brown |
blue-black |
yellow-brown |
| Biuret test |
blue |
violet |
blue |
blue |
| Ethanol emulsion test |
clear |
clear |
clear |
milky white |
Which option correctly describes the contents of sample X?
Select one option.