Why might there be lines after the parent peak in a mass spectrum?

In a mass spectrum, the presence of lines after the parent peak is often due to the occurrence of different isotopes. Specifically, the carbon-13 isotope is a common contributor to these additional peaks. Most organic compounds contain carbon, and approximately 1.1% of all carbon atoms are carbon-13 rather than the more abundant carbon-12.

When a molecule is ionized in the mass spectrometer, the mass of the ion created can include the mass of a carbon-13 atom instead of carbon-12 for some of the molecules present. This slight difference in mass gives rise to a peak that appears at a higher mass-to-charge (m/z) ratio than the parent peak, which corresponds to the theoretical mass of the molecule made only of carbon-12 atoms.

As a result, the lines following the parent peak are indicative of the natural isotopic distributions, particularly the presence of carbon-13, which explains why this option is correct. These lines provide insight into the isotopic composition of the sample being analyzed.