A student analyzed a sample using thin-layer chromatography (TLC). The resulting chromatogram, alongside reference compounds P and Q, is shown below:

Which of the following statements is correct?
Sample S is a pure substance because one of its components has the same RfR_fRf value as Reference P.
The RfR_fRf value of Reference Q is 0.800.800.80, and the chromatogram shows that Sample S contains both Reference P and Reference Q.
Sample S is a mixture containing Reference P and an unidentified compound with an RfR_fRf value of 0.600.600.60.
Reference P is more soluble in the mobile phase than Reference Q under these chromatography conditions.