परमाणु अवशोषण स्पेक्ट्रोमीट्रिक माप (atomic absorption spectrometric measurements) के लिए उच्चतम संवेदनशीलता प्रदान करने वाला प्रकाश स्रोत और परमाणुकरणकर्ता (atomizer) का युग्म कौन सा है?

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Beer's law is a limiting law as it is applicable mainly for relatively low analyte concentrations. Reason R: At high concentrations, the extent of solute-solvent interactions, solute-solute interactions, or hydrogen bonding can affect the analyte environment and its molar absorptivity. In the light of the above statements, choose the most appropriate answer:

Which of the following elements is most commonly utilized as an internal standard in Flame Photometry?