A student performs paper chromatography on four different food colorings, WWW, XXX, YYY, and ZZZ, to determine their purity and composition. The resulting chromatogram is shown below:

Which of the following statements is correct?
The mixture YYY contains the pure substance ZZZ.
Both WWW and ZZZ are mixtures, while XXX and YYY are pure substances.
The mixture XXX contains the pure substance WWW.
WWW is a pure substance that is present as a component in the mixture YYY.