Which scan result shows that there may be two or more matches for the unknown substance?

• A. Multiple positive match
• B. Single positive match
• C. Mixture
• D. Similar match

Answer: (D)

When a spectrum is compared to a library, you’re looking for how clearly one candidate stands out. A single positive match means there’s a strong, unique identification. If several candidates seem plausible, the system may flag a similar match to indicate ambiguity. This tells you there may be two or more substances with spectra that closely resemble the unknown, and none stands out as the definitive identity. A mixture would suggest the sample itself contains more than one compound, changing the spectral pattern, rather than simply creating ambiguity among library entries. So the presence of a similar match points to multiple plausible identities for the unknown.