Spectrum A is the emission spectrum representation for strontium. So, the correct option is A.
The image shows the results of a flame test for strontium. Strontium has a characteristic red emission spectrum, so the flame test will appear mostly red.
Spectrum A is the most likely emission spectrum for strontium. It has a strong red line at around 670 nanometers, which is the wavelength of light that strontium emits most strongly.
Spectrum B has a weaker red line at around 670 nanometers, and Spectrum C has no red line at all, so they are less likely to be the emission spectrum for strontium.