Final answer:
The correct representation of lead with an atomic mass of 204 is ^204Pb, which has the mass number of 204 and the symbol Pb for lead. Option a
Step-by-step explanation:
The isotopic representation of lead with an atomic mass of 204 is expressed as ^204Pb option a. The symbol Pb stands for lead, and the number 204 represents the mass number (the total number of protons and neutrons in the nucleus). Given the other options, ^123Pb and ^122Zr have incorrect mass numbers for lead, and ^248Zr represents an isotope of the element zirconium and is not related to lead.